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Re: Engine Diagnosis Question

Posted: 10:09 am May 18 2020
by bikeman2502001
I also am leaning towards the recluse even 450's get hot when gearing taller, and it is a well known fact that slipping the clutch causes alot of heat the pro's really monitor this. As for the pictures the only thing i see is on the picture of the head the left side looks like the head gasket wasnt sealing around the kips as well as the other side and the water jacket isnt too far away from that. The head gaskets are of a shim type when properly torqued shouldnt cause any problems. When you get it all back together if it still fails a pressure test On very rare occasions
there could be a porosity some where in the castings its rare but ive seen it happen but lets see what happens with a top end rebuild and proper torque settings and no recluse. Happy trails

Re: Engine Diagnosis Question

Posted: 04:03 pm May 18 2020
by G22inSC
I have not ridden it since putting the stock clutch back in as it's been in a state of tear down at the moment. Just picked up my head, piston and cylinder from the local machine shop and I've got a little too much piston to cylinder clearance. Shop measured my cylinder at 66.0374mm and piston at 65.9384 which gives a clearance of 0.099mm. The acceptable clearance is 0.079-0.089mm. A "B" piston (65.95mm) will give a clearance of 0.0874mm while a "C" piston (65.96mm) will give a clearance of 0.0774mm. I'm leaning towards installing a "B" piston as a "C" appears it will be too tight according the specs from the shop manual. Which piston would you'll suggest?

On a side note, shop confirmed what I thought which is that the head does not appear to be warped. It seemed flat to me with my tools at home and they stated they did not see any light when placed on a machinist's plate/table.

I have not noticed any coolant blowing out the hose so I'm assuming it's an internal loss. If the head is not warped, the gasket was not "blown" and I do not have coolant in the trans oil then what other options (other than cracked water jackets) are there for coolant loss and having to repeatedly be topped off after every ride?

Re: Engine Diagnosis Question

Posted: 04:49 pm May 18 2020
by JimmyB
You might just be losing coolant out the top overflow tank tube of the overflow tank depending on how rough the terrain you might have been riding, I use to lose most of the coolant from the tank when filled to the high mark. I have just been filling it to the bottom step at the bottom of the tank for the last 16 years..

Re: Engine Diagnosis Question

Posted: 05:18 pm May 18 2020
by kdxsully
I’d go with a b piston too.

Re: Engine Diagnosis Question

Posted: 07:44 pm May 18 2020
by KDXGarage
Make a paper towel "diaper" for the end of the coolant hose to see if it is leaking coolant out of the overflow. I have read of several people over the years losing a touch at times.

Re: Engine Diagnosis Question

Posted: 08:24 pm May 19 2020
by G22inSC
Got a little more prep work done after work today. Colored the head with a sharpie and then lightly sanded it over a plate with sandpaper. Looks good to me. Got the cylinder and KIPS pieces cleaned up and ready for reassembly. Did notice something with the connecting rod. It looks like it got hot to me. It’s got a blue discoloring to it. Does anyone know if that’s normal or cause for concern? It doesn’t have any up and down play and side to side is within spec.

Re: Engine Diagnosis Question

Posted: 10:29 am May 20 2020
by pumpguy
Regarding your rod, IMO I wouldn't be concerned about the color unless it was in the bearings area; both of which look fine to me.

As for the head, I would do what you can to smooth up the roughness in the combustion chamber. Won't really affect performance much one way or another, but should help discourage carbon build up.

Re: Engine Diagnosis Question

Posted: 05:11 pm May 25 2020
by G22inSC
Just an update...everything is back together and working through a few cycles now when I have time. I will have to keep a close eye on the coolant level and see what happens. Crossing my fingers all is well and no more over heating issues with the stock clutch. Only time will tell.

Re: Engine Diagnosis Question

Posted: 10:26 pm May 25 2020
by doakley
I run an auto clutch and had a beast of a time with boiling out coolant UNTIL I got the clutch adjusted properly. Now I run a higher pressure cap, replaced the plastic plug in top of the left radiator with metal oil pan plug (had to retap threads in radiator) and run Evans waterless coolant. I also overfill the trans with ATF to help dissipate heat. The bike definitely runs warmer, especially in tight, woods single track. Especially if I run in a bit too tall of a gear, which I tend to do, forcing the clutch to slip
More. But the boiling over has stopped. I’m happy with it now and do not want to give up the Autoclutch.
Also just pulled my top end for a preventative top refresh before resuming racing. It was very clean and looked fine with no evidence of heat damage.

Re: Engine Diagnosis Question

Posted: 03:59 pm May 26 2020
by G22inSC
I've done two heat cycles now and had to top off the coolant each time after the engine completely cooled. First top end I've done on a adult size bike with dual radiators. Followed the fill procedure in the manual and cracked the bleed screw in the top of the head. Every other top end I've done filling the radiator to the neck was all it took. I wonder if the cooling system is still trying to completely fill itself and pulling coolant from the recovery tank as it cools or is there still a internal leaking problem. Have you'll ever had to top off a few times after a rebuild or just fill the radiator and it's all good?

Re: Engine Diagnosis Question

Posted: 05:21 pm May 26 2020
by JimmyB
How much are you losing from the overflow tank when it cools? With the bike on the side stand, just usually fill up the rad, crack the bleeder screw on the head, top it up and good to go.
Have you done another pressure test, could it possibly be a leak inside around the exhaust port when the motor gets up to temp? Might flow into the pipe and slowly burn off from the heat?
Maybe take off the exhaust and just install it with minimal hardware, springs and a muffler bolt, bring the motor up to temp, quickly pull the exhaust off and pressurize the cooling system and see if it might come out the exhaust port??

Re: Engine Diagnosis Question

Posted: 05:33 pm May 26 2020
by G22inSC
JimmyB wrote: 05:21 pm May 26 2020 How much are you losing from the overflow tank when it cools? With the bike on the side stand, just usually fill up the rad, crack the bleeder screw on the head, top it up and good to go.

That is essentially what I have done but I also filled the recovery tank to the middle between "Low" and "Full." I have run it twice on the stand now and each time after cooling back down the level in the recovery tank was down to "Low" and I filled it back up to the same prior level.

I have not done another cooling system pressure test at this point. If this continues I will have to. My only guess at that point would be a cracked water jacket that is leaking once the cylinder heats up. I sure hope that isn't the case. Crossing my fingers the system is still just trying to fill itself.

Then again maybe I'm just paranoid at this point and watching it too closely.

Re: Engine Diagnosis Question

Posted: 08:05 pm May 26 2020
by KDXGarage
exhaust gas analyzer for cars to check

Re: Engine Diagnosis Question

Posted: 08:15 pm May 26 2020
by G22inSC
KDXGarage wrote: 08:05 pm May 26 2020 exhaust gas analyzer for cars to check
I wish but don’t have the funds for or access to one of them.

Re: Engine Diagnosis Question

Posted: 10:24 pm May 26 2020
by JimmyB
G22inSC wrote: 02:34 pm May 17 2020 Finally got a little time to do some more work. Got the top end off and found a cylinder with no scratches and a very clean head and piston. In my opinion, they are too clean like they have been steam cleaned by coolant. Didn't find any noticeable gasket issues but I don't really know what I'm looking at there. KIPS was all good but dirty. Going to take the cylinder and piston to a machine shop and see if I can get a good measurement on it all. Here is a couple pics of the head and top of the head gasket at time of removal. What do you'll think from the pics?
Sorry the quote didn't include the photos.I am just wondering, In your second photo just around the lower KIPS hole in the head was that moisture ?

Re: Engine Diagnosis Question

Posted: 10:36 am May 27 2020
by G22inSC
JimmyB wrote: 10:24 pm May 26 2020Sorry the quote didn't include the photos.I am just wondering, In your second photo just around the lower KIPS hole in the head was that moisture ?
Around the subvalve circular hole? If so, yes but couldn't tell if it was an oil/gas mixture or oil/coolant mixture. I could be wrong but I'm assuming it was excess pre-mix from a rich carb. Is that NOT normal/typical?

Re: Engine Diagnosis Question

Posted: 11:36 am May 27 2020
by JimmyB
Most likely is some pre-mix, just bleeding out and beaded up as you pulled the head off..

Re: Engine Diagnosis Question

Posted: 09:33 am Jun 05 2020
by Wesalauzen
well, I must not have read all the way through things : ) was commenting on an earlier post thinking you were still looking for guidance on the disassembled parts.

When you first fill a cooling system, there will be air that needs to work it's way out. . it may take a couple times to bleed it out, but then it should level off. I would pressure test it again if you can. Easiest way to know. If pressure drops, look around and see if you see any external leaks, at the head, hose ends, radiator, cap, etc.

Seems like you'll either be leaking externally which should be visible when pressurized. or internally which you should notice in your exhaust (whiter than usual, indicating steam).

A bad cap can cause issues and coolant loss also. It keeps pressure and keeps the system from boiling over. if it doesn't hold pressure, you will get overheating and coolant loss.

Not sure if any of this is new info, but just in case it's helpful.

Re: Engine Diagnosis Question

Posted: 04:42 pm Jun 05 2020
by G22inSC
Just an update for everyone. I needed a top end and glad I pulled it apart to do so and clean the KIPS. I believe I have probably tracked down the last issue...cross your fingers. Just the other day I noticed coolant around the neck. Did a pressure test on the cap and noticed it releases at the correct pressure; however, it does not hold pressure. Swap caps with my youngest boys KX65 and ran great with no coolant loss. Went back to my cap and once again had coolant loss. Couldn't see any external leaks but could easily be loosing coolant to evaporation. Have a new cap ordered from RMATV but it's backordered so it will be a little while. I will update everyone once I can. Thanks.

Re: Engine Diagnosis Question

Posted: 09:40 pm Jun 05 2020
by KDXGarage
GREAT TROUBLESHOOTING! Congratulations on getting it apparently solved. :bravo: