Rear Shock questions and Ideas

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Rear Shock questions and Ideas

Post by Chopperpilot »

I have a 2001 KDX 200. Last summer (short here in Alaska), I got much better at off road riding techniques and hill climbs. I've already grafted a set of 93' KX250 forks to the KDX and will either gold valve them this winter and/or try putting on a 2003 YZ250 front end that I got a crossover bearing to fit the KDX frame. I'm pretty decent at rebuilding and shim stacking for suspension (I first learned this on mountain bike forks and shocks).
Anyway, onto my question. I've read a lot from Chuck78 and SS109 on fitting Showa suspension pieces to the KDX (notably the rear shock). I have 2 dirt bikes, the KDX and a 1996 KLX 650R (I rebuilt the forks on this bike with gold valves). I have a good feel for what I want out of a fork, but am looking this winter to spruce up the rear end of both these bikes. Both bikes have essentially the same shock on them, which everyone agrees is 'a pretty decent shock'. Having never tore down or done any maintenance to the rear of these bikes, I'm sure just a standard rebuild/grease will show significant improvement, but what's the fun in that? So I'm going to either install gold valves in the shocks, or replace the 'pretty decent shock' with Showa 50mm versions (probably also gold valved or shim swapped at least). I'm curious from people here who have modified the rear end, will a Showa (rebuilt and valved nice) be that much of an improvement over a Gold Valved KDX shock? I think the improvement I'm looking for, or hoping to get, is better stability/tracking when climbing hills with semi large rocks (basketball and bigger) on them. Something that will 'float' over these things with a little less commotion than I currently have. I've heard the Gold Valves (and recommended shimming) should do this exact thing....... will a Showa do it that much better?
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Re: Rear Shock questions and Ideas

Post by KDXGarage »

I can't remember. What have you already done to the shock?

What is your weight in full riding gear and the current shock spring's rate?
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Re: Rear Shock questions and Ideas

Post by Chopperpilot »

I've done nothing to the rear end at all. I assume I have the stock 5kg spring on the KDX. In full gear I'm about 200lbs.
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Re: Rear Shock questions and Ideas

Post by KDXGarage »

I think you will need the 5.2. It will ride better after proper linkage / bearing maintenance and fresh oil and nitrogen. Don't place too much faith in your current worn out setup to make decisions off of.
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Re: Rear Shock questions and Ideas

Post by Chopperpilot »

Noted and thanks! I ordered 2 of the Gold valve kits for the KYB 44mm shocks (the KLX650r essentially has the same shock). I'll just rebuild and gold valve both of them. I have two Showa 50 mm shocks I got cheap off ebay (1 DRZ400 and 1 RM125) and I'll tear them apart at the same time to see if I notice anything worth the extra expense in fitting to either bike. I'll also check to see if either will easily fit to either bike. I suppose I can also actually check sag and race sag on both prior to disassembly and see about springs for either if necessary.
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Re: Rear Shock questions and Ideas

Post by KDXGarage »

Good luck with it all. Congratulations on getting the Gold Valve kits. It will take a lot of guessing out and should get you in very good shape.
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Re: Rear Shock questions and Ideas

Post by Chuck78 »

Regarding the 44mm KYB vs 50mm Showa, critics really praise the 50mm KYB on the 2024 Beta 200RR Race Edition, and talk bad about the standard 200RR & older model years of the 200RR Race Edition - citing the 46mm(?) Sachs shock doesn't have enough fluid capacity or shim stack diameter/surface area to really be competitive... It's all relative though, as a KDX guy that lives his KDX200H with Race Tech Gold Valves in the stock suspension (44mm KYB shock) also was saying this same thing that the Sachs 46mm shock was too small versus the new Beta model 50mm KYB shock...
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Re: Rear Shock questions and Ideas

Post by Chopperpilot »

Ok, stripped a lot of the bike down tonight. I guess I'm lucky! the rear linkage looks to just need a cleaning and repacking, everything still actually moves! The rear shock has some oil on the shaft, so it's good I was going to overhaul it anyway. So right now I have 3 ebay shocks, a DRZ, a 2005 RM, and a 2006 YZ (I was hoping to get the titanium spring, but accidentally made an offer on the wrong one!). I also wanted to see if maybe the YZ 46mm body could be adapted to the KDX shaft easily for something better than the 44mm KDX shock body. Well comparing the two, the reservoir on the YZ comes down way too far to be of use.
Now, comparing the DRZ shock to the KDX..... it's only a touch longer, and if I redrill the clevis from the 2005 RM and build the DRZ shock with that, I think it'll be very very close to KDX length. I'm definitely going to experiment with that.
I was happy that all the linkage bolts came out easily, and were clean with a little bit of lube on them. Even the swingarm bolt came out easily.
I just need to find a service/rebuilt kit for the 44mm KYB shock now.
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Re: Rear Shock questions and Ideas

Post by KDXGarage »

Technical Touch has the parts. They are sky high now!
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Re: Rear Shock questions and Ideas

Post by billie_morini »

Of course, the parts price is sky high! Just bought 2 performance tires for my supercharged MINI Cooper. The price for 2 of these tires was enough to purchase 4 tires the last time around. :evil:
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Re: Rear Shock questions and Ideas

Post by Chuck78 »

Chopperpilot wrote: 11:59 pm Jan 25 2025 Now, comparing the DRZ shock to the KDX..... it's only a touch longer, and if I redrill the clevis from the 2005 RM and build the DRZ shock with that, I think it'll be very very close to KDX length. I'm definitely going to experiment with that.

Cool, that sounds like a pretty excellent combo from the parts you have!

Based on your other thread, I'm thinking some of those Yamaha triples that have the longer steering stem (is the 4mm shorter stem going to still work for the KDX frame? Seems you thought the 2003 steering stem would be too long but it ended up working?), if there is a Yamaha WR250 fork that fits in that or if the WR250 steering stems are good for the KDX frames with those special size 12mm tall conversion bearings, then this is really perhaps the ultimate setup for a KDX swap, hands down!

I suspect that some of the KYB 46mm 1994-ish-2005 KX125 shocks may also work out very well to fit the KDX to match a Yamaha WR250 fork's ride height...and the WR250 off-road models will already have decent woods valving for trail use...

Similarly, I'm thinking the '96-'97 RM125 Showa 46mm shocks could also be the best Showa shocks to swap, but if my crankcase clearancing works out well, I'm absolutely running my 50mm "FrankenShowa" shock build and it's titanium spring that I picked up...

By the way the Yamaha OEM Titanium springs were not of the best reputation, with people cracking them due to alloy content issues. Diverse Spring lightweight Silicon-Chrome springs are the best bet, as the good RCS (Renton Coil Spring) Titanium shock springs are $499 new...
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Re: Rear Shock questions and Ideas

Post by Chopperpilot »

I read a lot that seemed to point any factory YZ titanium springs cracking was due to these plastic clips that are on each end to prevent it making contact with itself. Apparently they fall out mildly regularly and if you just ignore it, you can break the titanium spring.
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Re: Rear Shock questions and Ideas

Post by Chopperpilot »

So, after getting the YZ front forks squared away and pulling the top end off to see what it needed (sending it off for a replate and might as well do the big bore while there) I started on the rear shocks. Right now I just have the KDX shock dismounted and I squeezed a 2003 DRZ shock in it's place to 'see'. Today I disassembled the two Showa shocks (2003 DRZ and 2005? RM 125) to see about swapping up parts in them. The 2005 RM shock has the longer clevis, but looks to be able to be drilled to a shorter overall length than the DRZ setup. The DRZ has a shorter body though. Well here is the DRZ body with the RM shaft (larger 18mm shaft). The red circle is a mark I made where I believe the clevis can be drilled for the KDX knuckle without having to clearance anything. A slight bit more could be had with some beveling/sanding.
IMG_1688.jpg
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Anyway the DRZ body with the RM shaft, if the RM clevis is drilled to a shorter overall length looks to be like it could be within 5mm of the KDX length.
I also had gotten a YZ shock off ebay with the intent to see if the 46mm body could be used with the KDX shaft, it cannot, the reservoir is way to long on it. I then wanted to see if perhaps the spring was a slightly smaller diameter but would fit on the Showa, and reduce the interference with the engine case at top out, this will not work either. The spring outer diameter appears to maybe be a couple mm smaller than a showa spring, but the ID prevents it from being able to slip over the showa bottom spring retainer piece that stays on the shaft. So now I will just see if maybe the HS compression adjuster can be put onto the KDX shock, maybe?
Having the Showa shock be the same length as the KDX shock will definitely ease up on the clearance required of the engine case as the knuckle moves further away at shorter lengths.
My next move will be to take apart the KDX shock and compare total travel (minus bump stops) between the KDX and the Showa DRZ/RM combo. One interesting thing is that the RM shaft is noticeably longer than the DRZ shaft. The RM seal head had a top out spring that limits the free extended length of it and the DRZ seal head did not have this. I'll also use my drill press and drill the clevis out for the shorter length. I figure I can tap the other side just like the KDX setup so that there's no need to put a nut on the other side of the clevis.
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Re: Rear Shock questions and Ideas

Post by KDXGarage »

Please be aware of "inside the body" length of travel. I am seeing the rear tire go through the fender and eat the toolbag.

Install them without springs and check travel.
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Re: Rear Shock questions and Ideas

Post by Chuck78 »

I wouldn't offset drill that clevis too much at all, it will generate more side load the shaft, which is not a good thing, but is workable to a certain extent, it will just place a little bit of added where on the shock body, piston band, and seal head. A slight bit should be fine but I would still consider clearancing the crankcase rear portion for the majority of the clearance.

The guy that has all of the race team KX450 parts for sale was heading out of town and doesn't seem to have had the time to measure the shock for me, but I think that 2024 KX450 shock could be quite workable and clear the crankcase on the KDX has it has a tall lower spring seat that completely encompasses the bump stop, and at bottom out, the shock body will be inserted deeply into this lower spring seat. I need to find out the length though as it advertises 2023 and 2024 as being 475 mm although they were completely different and I had read that the 2024 shocks were made shorter for fuel pump placement reasons and other reasons with the bike design.
These are very expensive forks & shocks though, most people are absolutely not going to want to spend the money for 1-year-old race team take off parts from current models when rebuilding their KDX.

I'm very curious to see how the longer RM clevis from the 2005 and up or KX250F 2006 and up would clear especially when combined with that DRZ400 body.
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Re: Rear Shock questions and Ideas

Post by Chopperpilot »

Oh, I'm not going to offset drill (I didn't say that though). I just made that mark when I was sliding the knuckle into the clevis. I wanted to accurately eyeball the center of the hole in the knuckle and make a vertical reference point on the clevis for where the centered hole would be.
Possibly a touch higher with clearancing the clevis and knuckle some.
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Re: Rear Shock questions and Ideas

Post by Chuck78 »

If you are putting a longer shaft in the shorter body, I personally would look into some of the extended piggyback reservoir and caps so that you can have a little bit more volume of nitrogen in there so that the reservoir can take up the extra amount of fluid being displaced from a longer shaft and shorter body. Race check sells them, then there's a generic that's very similar, and then MX Tech or someone sell some that are a burnt bronze type brownish color, goldish brown I don't know how to describe it. There are at least 10 different configurations of the caps depending on what bike. I found a chart showing all of them but I can't remember which website it was on
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Re: Rear Shock questions and Ideas

Post by Chuck78 »

I've gotten a good deal eBay seller offer, so I snatched up a '96 RM125 46mm KYB shock as well...purchasd yesterday on eBay, arriving TOMORROW!
Allegedly these are 444mm length according to the Teknik Motorsports website, which is right around the absolute maximum usable length for the stock KDX frame shock mount location and stock rocker linkage, while being 46mm piston size vs the others we've been working @ a modern size of 50mm, with that are best off with some filing/grinding to clearance the back of the crankcase in a thick and non-significant area, these '96-'97 46mm Showas look to not likely need any clearancing, and may fit length-wise with maybe a 2mm lowering spacer internally at most, or none at all! I'd bet a similar era '96-'98 or '99-'02 KYB from a KX125 would be a fairly similar fitment. KYB didn't move up to 50mm shocks until several years later.
The 50mm is the golden standard in these modern times, but I feel a 46mm will not leave an average woods rider much of anything to complain about at all... and the compression adjuster assembly looks to be the same still, so a 2002+ DRZ or 2001+ RM etc would probably be able to swap the dual compression adjuster in place of the single adjuster, but really the Lainer Suspension '08+ KX250F Showa adjuster looks to fit the '98 RM just fine, and the '96 adjuster looks identical to the '98. I may try to get a 2006-2008 YZ125 OEM Yamaha Titanium 4.8kg spring and open up the lower spring seat inside diameter (they taper inwards) to run a budget used titanium spring on this 46mm shock as well...
The 50mm FrankenShowa is still definitely going onto my '99 KDX220 since that one's not in riding condition now and engine and whole bike due for a complete overhaul, so that frame's shock mount will get chopped up to move the upper mount rearward 6mm and upwards 14mm-16mm... The swingarm pivot/engine mount combo bolt area of the crankcase still needs clearanced/shaved for topped out spring clearance on the 50mm Showas, but the engine case is 10mm thick around the first 25mm left and right, and the center section where the clearancing is needed is 7mm thick roughly. This shouldn't be any issue. I can JB Weld the inside of the case there when I have them split if there's any question of strength, but Kawasaki hollowed it out from the inside out in the center area of the cases, so I highly doubt this will be any issue.

The '97 RM125 is also a 46mm shock, but listed as being 447mm length from Teknik (vs 444mm for the '96 version), and they do carry a different part number '96 vs '97, so that may perhaps be correct (their measurements are occasionally slightly erroneous, so I have found).

With that and KLX300 117mm pull rod links, the KDX will sit around a hair under 1" higher in the rear than stock, which is really about perfect for the KDX for riders 5'10" and taller, more ground clearance and more available travel.


I'm also pretty close to pulling the trigger on some 2022, 2023, or 2024 KX450X forks on ebay... I have a triple clamp set in the mail which I'm fairly confident will be very workable on the KDX frame with a conversion upper bearing size, and modifying the steering stops. So we now have CR/CRF, YZ250 2-stroke and *some* WR250, YZ450F, YZ250F triples, and 2019+ KX 4-stroke triples that are the right height for our KDX frames, and as of late have available 28mm and 30mm i.d. 47mm o.d. conversion bearings available! This is a big breakthrough...
I need to find a better set of lowers for my '97-ish KX500 forks (hoping to upgrade to a '99-'02 set of KYB 46mm lowers) and sell them as a KDX bolt-on package deal upgrade before I tell too many people about these new fork swap options! Steering stem swaps as I always say seem like a shame to downgrade to a hefty steel stem and machine shop knurling and bushing making just to get modern forks, these new options will allow use of the aluminum steering stems to keep things simple and save a lot of weight...
I was blown away that some fork swap UPGRADES to generally all LARGER diameter forks that are MORE RIGID, would drop 3, 4, even 4.5 lbs off the weight of the KDX! I'm still running the -1/2lbs weight savings 1998 RM125 forks on one of my two bikes though... RIght side up conventionals... I sure wish Showa would just remake a modern version of those Twin Chambers, or just a lightened up + mid-valve added version of the open chamber variant on the 2000-2024 DRZ400...
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Re: Rear Shock questions and Ideas

Post by Chopperpilot »

OK, got some interesting data today. All this was measured from the frame on a stand with forks and front wheel on, and using a tape measure at the end of the swing arm from the garage floor. Looked at swing arm travel without a shock mounted and found that the dog bone links (pull rods) limit upper travel if the shock doesn't. With a 110/100 shinko 505 (fresh) and pulled all the way back on the swing arm (not realistic) the dog bones prevented the tire from stuffing into the fender, just lightly scraped an edge. I believe total swing arm travel was somewhere around 14". Droop was stopped by the knuckle hitting the frame. You really see the progressive nature of the linkage system when you watch the knuckle horn (where the shock would mount) move about 1:1 at full droop and then rapidly moving much faster than the swing arm the further up the travel you go.
I then mounted KLX650R 115mm dog bones on it and found that they essentially moved the swing arm up 1/2" apparently at the top and bottom of travel. The tire would stuff into the fender with significant interference (again with no shock mounted).
Next I installed the RM shaft into the DRZ showa body and installed the clip to hold the seal head in place (no spring or oil or reservoir bladder). Because I found that up travel was limited by the tire/fender/dog bones, I drilled the RM clevis slightly longer than I previously thought about, trying to get a little more height/ground clearance/maybe travel (but still shorter than the DRZ shock setup). This ended up with 3/4" gain in 'ride height'. I had to bevel the RM clevis to allow full shock droop to be the stopping point instead of the clevis hitting the knuckle. Next I checked travel and here's where things got 'interesting'. Total swing arm travel (with the frankenshowa fully drooped out) was only 9"! Now the piston stack/seal head are 'taller' on the RM shaft vs the DRZ, the RM shaft is also longer than the DRZ shaft. The RM shaft was still able to go fully into the shorter DRZ body though and appeared to stop when the top of the clevis hit the cover of seal head. I'm not sure what to make of this, I'll probably try the full DRZ setup in the bike and see what that does for travel, but eyeballing the two shaft setups, I don't see the extra 2.8" of travel by using the DRZ shaft (isn't the KDX supposed to have 11.8" rear?). So next thing will be taking the spring off the KDX shock and mounting it in the frame and seeing the 11.8" of travel. Full disclosure, I used a tape measure but was still eyeballing everything, so if we were talking about a 3/4" discrepancy, I would blame my non precise measuring technique. Oh the RM/DRZ shock combo had 118mm of shaft exposed for travel.
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Re: Rear Shock questions and Ideas

Post by Chuck78 »

I was up late last night doing a very similar experiment, I actually sent you a private message about it probably about the same time you were posting this!
I'm not sure how you were getting only 9 inches of travel with the shock mounted though, vs 14" with the axle all the way back in the swing arm and no shock?

I was quite surprised to look at the difference in rear wheel travel from axle in its current position with a short chain, on the third shortest chain adjuster notch, to having the axle back just one inch from there or all the way back. This tells me that just running a longer chain requires a fair amount of work on the suspension clickers on the shock, which I never even considered before.

I also realized that with the 117mm pull rod dog bone links from the KLX 300, I was only getting a little over 100 mm travel on the shaft of the stock shock, whereas the shock would bottom out on itself prior to my other startling discovery, the swingarm actually bottoms out the chain up against the upper chain roller prior to the tire hitting the fender. The swing arm and swing arm chain buffer will actually sandwich the chain up against the upper chain roller slightly prior to the rocker linkage reaching its maximum extension to the point where all three pivot points would be directly in line and the swingarm compression motion upwards can no longer travel any further upwards because the linkage geometry is at maximum extension with all three pivot points in a straight line instead of a rocker type configuration. This made me realize that people that want to lower a KDX really should be adding some bottom out bumpers or just using a seal head lowering spacer or internal shock lowering spacers in conjunction with a shorter link. 117mm in my opinion would be the absolute maximum length lowering link to use unless you were going to relocate that upper chain roller tab on the seat subframe removable bar maybe 10mm+ higher & run a stock size 100/100-18 tire vs the 110/100-18 that is commonplace.

This is where I was really thinking you late night in my shop for tipping me off on the 115mm KLX650R pull rod dog bone links. I really feel that 114mm-116mm would be most ideal for these longer shock setups.


So with the 117mm pull rod dog bone links from the KLX 300, I was only getting a little over 100 mm travel on the shaft of the stock shock.

With the stock 112.5mm links, with the stock shock again, I was actually able to bottom out the shock lower spring perch against the seal head bump cap slightly prior to the rocker knuckle linkage and swing arm pull rod pivots all three being inline directly with each other which is when the swing arm can no longer travel any further up because it is mechanically limited at full linkage extension. This was also slightly before the swingarm would bottom the chain into the upper chain roller. So with this setup, I had far more shaft travel than what I could possibly use. With full rear wheel travel with no shock mounted, from full droop to swing arm bottoming chain against upper chain roller, I measured 133mm of available linkage/shock travel if I'm remembering correctly. This is not possible with any of our options - although the '98-2000 RM shocks have that exact amount of travel, but are too long to be able to utilize it in this frame which, as stock & with a clearanced shock knuckle, the maximum usable shock length is just a hair over 438mm from my latest measurements. I believe that's pretty accurate although I absolutely have some old used linkage bearings although none of them seem terribly sloppy, it only takes a little bit of slop to introduce a lot of rear wheel travel slop.

Switching to the KLX650R's 115mm links, I found a happy medium of the long travel setup. With this setup and the shortest combination of my shock parts, the DRZ400 or '98(-'00?) RM bodies, using the shorter '01-'04 RM125 clevis with my heavy beveling on the inside part of the crotch as well as removal of casting flash from The rocker knuckle and using a Dremel stone to create a dimple in the end of the rocker knuckle for the screw on the bottom of the clevis to clearance into at full droop, here I was able to utilize 123mm of shaft travel. I believe this is where I measured 12.75 inches of wheel travel? And my observations, unmeasured, would support the fact that there could be 14 inches of total wheel travel available with the axle all the way back in the swingarm axle dropout slots.

My biggest takeaway was that I was incorrect in my assumption the other day that longer suspension links really only alter the swing arm position, not the geometry, was completely wrong! Clearly this experiment showed me that there was a difference of almost 30 mm shock shaft travel between 112.5mm links and 117mm links...
And also that the upper chain roller is the first limiting factor with 117 links, big surprise to me! I think I'm going to get some stainless steel bushings that are slightly larger OD than what the sleeve bushings are in the KLX links, but same ID, and offset drill the holes to reduce them in effective distance to try and make some 114.5mm links out of them.
So what I realized out of this was that the valving and spring rates are drastically affected by a 4.5 mm change.... Now with 115mm links, I feel the 4.9 kg titanium spring that I have will be right on the money. I was looking for 4.8 at the time and I thought race checks calculator was crazy for telling me I needed a 4.6 when I was "happily" (ignorance is bliss?) running a 5.0 stock with preload backed out considerably.

These longer links at 115mm + the further rotation of the rocker knuckle linkage beyond what the stock shock allows will both give the swingarm and linkage a noticeably different leverage ratio that might actually work well with the RM 125 shock valving to make it a fairly plush setup for woods riding with only a little shimstack altering, as best as I can speculate. Just calculating leverage ratios fairly crudely with available shaft travel on the shocks I have without the bikes in front of me, versus the advertised wheel travel on those bikes the shocks came from, the DRZ would have the softest shock valving versus the leverage ratio. RM125 next, KDX last (more firm valving required of leverage ratio).
Running the axle further back as I plan to do on my next chain install will soften the action of the suspension even more, as you will get even more wheel travel for the same shaft travel....
'97 KDX220R - purple/green! - KLX forks, Lectron, FMF, Tubliss
'99 KDX220R project - '98/'01 RM125 suspension, Titanium hardware, Lectron Billetron Pro, Tubliss
'77 Suzuki PE250 & '83 Suzuki PE175 Full Floater - restomod projects
'77 Suzuki GS750-844cc, '77 GS400/489cc & '77 GS550/740cc projects
'62 GMC 1000 Panel Truck
'88 Suzuki Samurai TDI/Toyota swaps
'88 Toyota 4x4 pickup
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