85 Big Red 250es hard starting - Rebuild time?

[ps2fixer]

The chain is the part that likely has the most wear. Chains don't look ugly when they are worn, they stretch over time, the wear you don't really see visually. Since it's apart, a new chain is normally a good idea. Kind of like on a car, when you do a timing belt job, you also replace the water pump since you're already right at it.

I looked up the maintenance schedule and it seems like long didn't give a service life for the timing chain. I scanned around a bit and the only thing I found about the timing chain for checking it is inspect the slides for damage and make sure the tensioner is functioning correctly. I guess they pretty much are suggesting the chain is good for the life of the engine. Personally I'd replace the chain since they aren't normally too expensive, and you'll be good to go for 20+ years for internal engine work if all else is in good shape. The chain normally gives a nice warning when it's about to cause problems, it gets loose and you get a "timing chain slap" noise in the engine. I haven't really heard about them going bad on the 250es, but I've seen them go bad on the atc350x, trx250x and such and the past owners ignored them.

Does the cam chain slides have damage? There's going to be visible wear from the chain sliding on them. If there's excess wear it should be replaced.

Measure the cam and rockers, if they are in spec, they are good to use.

[Epic69]

The chain is the part that likely has the most wear. Chains don't look ugly when they are worn, they stretch over time, the wear you don't really see visually. Since it's apart, a new chain is normally a good idea. Kind of like on a car, when you do a timing belt job, you also replace the water pump since you're already right at it.

I looked up the maintenance schedule and it seems like long didn't give a service life for the timing chain. I scanned around a bit and the only thing I found about the timing chain for checking it is inspect the slides for damage and make sure the tensioner is functioning correctly. I guess they pretty much are suggesting the chain is good for the life of the engine. Personally I'd replace the chain since they aren't normally too expensive, and you'll be good to go for 20+ years for internal engine work if all else is in good shape. The chain normally gives a nice warning when it's about to cause problems, it gets loose and you get a "timing chain slap" noise in the engine. I haven't really heard about them going bad on the 250es, but I've seen them go bad on the atc350x, trx250x and such and the past owners ignored them.

Does the cam chain slides have damage? There's going to be visible wear from the chain sliding on them. If there's excess wear it should be replaced.

Measure the cam and rockers, if they are in spec, they are good to use.

I never heard any chain slapping while running it before. I do see the chain guides have wear but I have nothing to compare to. At this point opening the case up and pulling all the clutch and such is scary. I will measure the cam and rockers. I been looking for a good youtube video on how to do this and am not finding any...

[ps2fixer]

It's not bad you just have to take your time. If I recall correctly the crank nut is reverse thread (left handed). Besides that,should be able to do the job with only pulling the primary clutch, but maybe the secondary conflicts some how. Been a long time since I pulled apart a 250es engine.

[Epic69]

It's not bad you just have to take your time. If I recall correctly the crank nut is reverse thread (left handed). Besides that,should be able to do the job with only pulling the primary clutch, but maybe the secondary conflicts some how. Been a long time since I pulled apart a 250es engine.

Ok assembly going well, have Jug on and Head on now torqued down to specs in service guide. Next i'll get the chain and gear alilgned with TDC and tightened down. Reading ahead in service manual says 'use sealant' on head with rockers.. what type of sealant should I use there I have no idea? Its the cover that has the rockers in it.

[ps2fixer]

Most people would swear by Hondabond, but you can also use the GRAY RTV that parts stores carry. Both cases, apply thin and torque down to spec. Both are effectively a glue, Hondabond sets up hard like a weak jb weld while the gray rtv setups up firm but not solid. There's also another brand, but I can't recall off the top of my head what it was. My dad's experience with it is it sets up so fast you don't get enough time to assemble and it doesn't seal. Context for that was chain saw base gasket delete and they failed the lead down test until he switched to gray rtv and no more problems. No personal experience with any of them, just blurting out what I've heard.

From the factory, it had Hondabond, or something very similar so that's generally a good route to take, pretty sure you'd have to stop in a Honda dealer to get it though. Yamabond is effectively the same stuff too.

[Ottoscorch]

I never heard any chain slapping while running it before. I do see the chain guides have wear but I have nothing to compare to. At this point opening the case up and pulling all the clutch and such is scary. I will measure the cam and rockers. I been looking for a good youtube video on how to do this and am not finding any...

Watch Mustie1 on youtube he rebuilds these and many other types . Just watched a 125 get a jug and piston done by him .Quite simple actually