HopFrog's 1980 KDX175 Build Log

Discussion specific to the various air-cooled KDX models sold in the USA
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Re: HopFrog's 1980 KDX175 Build Log

Post by KDXGarage »

I don't think it requires alignment. It just finds the hole through pressure, I suppose.

I am going to be bold and state that I do not think you will be riding this wonderful KDX175 through a lot of mudholes, so it would not require constant regreasing. :-)
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Re: HopFrog's 1980 KDX175 Build Log

Post by HopFrog175 »


Well, that hollow bolt idea for greasing the swingarm sure seems good. I stared at the parts on the bench for a good long while but could not see how to make it work with the KDX175 bearings - so I cleaned, lubed and put everything back together.

If a cheap swing comes up, I may get it and use it to try ideas on - for now, I will be re-greasing manually after any mud-hole incidents or other submersion - hopefully rare in the desert :-)
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Re: HopFrog's 1980 KDX175 Build Log

Post by KDXGarage »

The desert?! HA! Yeah, I think you will be just fine without the grease fittings. I have full confidence that you will regrease on a schedule, not let it go for too long.
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Re: HopFrog's 1980 KDX175 Build Log

Post by HopFrog175 »


The engine is now pulled apart for crank seal attempt #2. The first attempt failed the leakdown test and air bubbles appeared around the outer edges of both seals.


Engine back apart
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kdx175_00_engine_apart.jpg
kdx175_00_engine_apart.jpg (359.8 KiB) Viewed 5567 times


With the crank out, it seemed to be a good time to think about bearings. Although bouth had a good feel, one came with the bike and one was a replacement - both from about 30 years ago. Replacing with Timkens (6305) is easy at this point. Step one - remove the old bearings with a bearing splitter and press.


Old bearings coming off
kdx175_01_bearing_removal.jpg
kdx175_01_bearing_removal.jpg (346.83 KiB) Viewed 5567 times


The new bearings matched up so the crank was taken to the freezer.



New bearings - 6305
kdx175_02_timken_bearings.jpg
kdx175_02_timken_bearings.jpg (348.33 KiB) Viewed 5567 times


Here is an inside view of the errant holes a previous owner drilled through the crankcase (possible for bearing removal). They look nicely sealed :grin:


Plugged holes behind bearing
kdx175_03_holes_filled.jpg
kdx175_03_holes_filled.jpg (187.12 KiB) Viewed 5567 times


Now is a good to clean off the red Loctite sealant while the crank is freezing. I like Locktite products but am doing some research about sealants - I may end up switching.


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Re: HopFrog's 1980 KDX175 Build Log

Post by KDXGarage »

any thoughts to take the case half to have it TIG welded and sanded down?

Molly's 70 on here is a welding guy. See what he thinks.
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Re: HopFrog's 1980 KDX175 Build Log

Post by Molly's 70 »

That might be a tough one to get the tig torch positioned right & still be able to see what your doing. I need more pictures of both sides.
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Re: HopFrog's 1980 KDX175 Build Log

Post by KDXGarage »

Thank you for participating on kdxrider.net. :bravo:
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Re: HopFrog's 1980 KDX175 Build Log

Post by Molly's 70 »

OK, I went back to refresh my memory. I think I could get to it from the outsides of the cases. It would be nice to have closer-up pictures.

However, If those holes were plugged with JB Weld,(I think I read that) its pretty much a "no-go" unless every bit is removed. In fact, JB weld might be a good solution in this case.
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Re: HopFrog's 1980 KDX175 Build Log

Post by HopFrog175 »

any thoughts to take the case half to have it TIG welded and sanded down?


Thanks for the suggestion, this is a good idea. Here is a closeup before JB Weld.


1 of 3 holes
_click image to zoom_
kdx175_00_errant_hole.jpg
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hf175w.jpg
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Re: HopFrog's 1980 KDX175 Build Log

Post by HopFrog175 »


Welding the little crankcase holes

The first step was prep, grinding out all of the JB Weld that I initially used to plug the holes. At the time, the engine was mostly assembled so JB Weld was the easy choice. Now, that the engine is back apart (to try for a better crank seal install) the suggestion to weld those holes was apropos. Drilling out the holes one size larger got all of the JB Weld out.


Weld prep
_click image to zoom_
kdx175_01_holes_to_weld.jpg
kdx175_01_holes_to_weld.jpg (359.79 KiB) Viewed 5334 times


I looked up an old buddy and he came to the rescue (thanks Kimo!). He plugged two holes from the outside.


Plugged holes
kdx175_02_welded.jpg
kdx175_02_welded.jpg (287.08 KiB) Viewed 5334 times


The third hole was buried in that narrow space so it was tackled from the inside.



Third hole - plugged
kdx175_03_inside_weld.jpg
kdx175_03_inside_weld.jpg (150.51 KiB) Viewed 5334 times


The inside weld needed to be smoothed down as the crank bearing mounts here. Fortunately, a bit of variation in this area should not be too critical - only a small part of the machined surface is effected and its purpose is to locate the bearing axially on the crank. A little drill press rigging was fine.


Cleaning up the inside weld
kdx175_04_cleaning_weld.jpg
kdx175_04_cleaning_weld.jpg (289.57 KiB) Viewed 5334 times


It came out great :grin: so I went ahead and pressed in the seals - making sure to use a sealer this time!


Cleaned up and new seals installed
kdx175_05_cleaned_up_new_seal.jpg
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Re: HopFrog's 1980 KDX175 Build Log

Post by KDXGarage »

Nice! Thanks for the follow up!
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Re: HopFrog's 1980 KDX175 Build Log

Post by HopFrog175 »


Well, now one more problem - while getting everything cleaned up assembly, i noticed that the gear on the clutch basket has some slop. Not a lot but definitely more than zero as the gear can be rotated a degree or two while the basket is stationary.


Clutch gear rotated right
_click image to zoom_
kdx175_01_loose_clutch_gear.jpg
kdx175_01_loose_clutch_gear.jpg (111.39 KiB) Viewed 5297 times

Clutch gear rotated left
kdx175_02_loose_clutch_gear.jpg
kdx175_02_loose_clutch_gear.jpg (144.76 KiB) Viewed 5297 times


Looks to be under half a millimeter or, maybe, 0.030" at the outer circumference. I think I am correct in assuming that any discernible movement is too much?

Keeping alignment while putting in new rivets seems like it would be hard (even if my press would do it), I may have to look around for a replacement clutch basket.

Well, better now than later I guess :neutral:


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Re: HopFrog's 1980 KDX175 Build Log

Post by Molly's 70 »

Good job on welding the holes in the case. Also, Good job on reworking welded area. It doesn't get any better! :grin:
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Re: HopFrog's 1980 KDX175 Build Log

Post by Slick_Nick »

You will need new clutch basket bumpers to fix that slop. You can drill and tap the rivet holes for some flat head hex machine screws once you remove the stock rivets. I've done this on a few vintage Suzuki baskets with success. Use loctite and peen the screws once installed.
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Re: HopFrog's 1980 KDX175 Build Log

Post by HopFrog175 »


Thanks Molly's 70 - all the welding credit goes to my buddy Kimo - he knows his stuff!

Slick_Nick, thanks for the suggestion, I already started removing the clutch basket rivets. My initial thought was to stop by the local rivet place and see how close of a match they had.

I like the idea of drilling and tapping though - mainly because I would be able to more closely match the tension of each fastener to some nominal value (compared to flattening the rivets, one at a time, by hand).



Pilot drilling a rivet with 1/16" bit
_click image to zoom_
kdx175_01_drill_rivet.jpg
kdx175_01_drill_rivet.jpg (275.14 KiB) Viewed 5199 times
kdx175_02_drilled_rivet.jpg
kdx175_02_drilled_rivet.jpg (258.9 KiB) Viewed 5199 times

Moved up to an 1/8
kdx175_03_drilled_rivet.jpg
kdx175_03_drilled_rivet.jpg (264.29 KiB) Viewed 5199 times

Chiseling off the rivet head
kdx175_04_drilled_rivet.jpg
kdx175_04_drilled_rivet.jpg (248.67 KiB) Viewed 5199 times


The rivets are about 0.160" diameter and somewhat over 0.422" in length. Hansen Rivets lists slightly under and slightly over. I imagine best to go slightly over and will talk to them. Then, I will check out screws.


Clutch basket rivet
kdx175_05_drilled_rivet.jpg
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Re: HopFrog's 1980 KDX175 Build Log

Post by KDXGarage »

"My initial thought was to stop by the local rivet place". I don't think I have ever heard that one. :-)

Keep up the good work!
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Re: HopFrog's 1980 KDX175 Build Log

Post by Slick_Nick »

I went down to my local rivet place when I did my flywheel rivets. They had hundreds of sizes in stock, likely ones that work for the clutch basket but I still elected to use screws for the last one I did, my old RM125. There's nothing wrong with screws if they're peened and loctite is used, will make replacing the bumpers in the future easier.
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Re: HopFrog's 1980 KDX175 Build Log

Post by HopFrog175 »


I got the rivets out and looked inside of the clutch basket:


Original Clutch Basket Rubber Cushion Bumper Dampers
_click image to zoom_
kdx175_01_clutch_disassembled.jpg
kdx175_01_clutch_disassembled.jpg (292.48 KiB) Viewed 5167 times


Now I see how this works. This is the first time I have had one apart and I have somehow never looked at pictures - I assumed it was solid.

And, I can see how the rivets just hold things together without transmitting any torque

The hard part looks to be sourcing the rubber dampers as I see about a half dozen Kawasaki versions exist. If anyone knows the right version, please let me know! I will do some calling around and see if someone can take some measurements too.


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Re: HopFrog's 1980 KDX175 Build Log

Post by Slick_Nick »

You might have to do some measuring and poking around some various manufacturer catalogs since there likely isn't a listing for a bike as old as yours.
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Re: HopFrog's 1980 KDX175 Build Log

Post by HopFrog175 »


Here is what I have found on the the rubber clutch dampers (cushions) for the KDX175:


KDX175 clutch damper (cushion)
_click image to zoom_
kdx175_01_cushion.jpg
kdx175_01_cushion.jpg (238.39 KiB) Viewed 5086 times


With help from HinsonRacing (thanks Robert!) it was determined that an exact match might no longer be available. The KX80/85 is pretty close but measures slightly larger. In particular, the inner "D" shaped hole might be too loose. Once I get the KX80 version in my hands, I will know for sure and, at that point, maybe I can shim somehow if it is too loose.

A better idea (or a closer replacement) would be welcome! Perhaps, given the correct rubber material, I could cut some on a laser cutter.


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