86' 350x keeps jumping time.

[Apeterson26]

I have replaced the timing chain, tensioner, anything else that was out of spec. Yet shortly after I get it all buttoned back up when I kickstart it, jumps time. Im sick of taking this thing apart any suggestions would be greatful.

[tapper190]

What does the sprocket on the crankshaft look like?

[Apeterson26]

As far as I can tell visually, it doesnt look bad. I see that one of my guides are bent and looks quite thin. I guess that means I have to pull the motor AGAIN. Anyone know if they make an aftermarket set of replacement guides?

[tapper190]

Did you replace the timing chain with an oem or aftermarket one from ebay?

[Apeterson26]

I replaced it with a DID chain, like $85

[oldskool83]

sprockets get worn after 40 years, lower one on crank is prob worn bad, or cam chain not adjusted proper. anytime you go intot a motor you just replace all the stuff since your already in. Ive had to take 1 motor back apart in 20 year due to something else needed, a bad head gasket that didnt seal. It's rare I ever do. If you think that head a piston are good either your prob running the gauntlet. Open a motor and do it all.

Ebay will have replacement cam chain guides, lower sprocket get pressed on the crank so prob need to remove the crank, once your that far deep might as well do a full motor rebuild. You'll find other stuff.

[ATC King]

What about the ignition? Flywheel key broken?

I don't know if an ignition kickback would be strong enough to cause that problem on that engine, but kickbacks can be strong enough to break parts, even on electric start engines, from mowers on up to cars and pickups. Two-cycle small engines with a bad coil can do it hard enough to break recoil starters.


Always inspect all new parts. I say it all the time and just got reminded of it with a new part I bought that wasn't assembled correctly. Even if it's a cam or crank gear, get out a good light and thoroughly inspect it. Same with a 'new' cam chain, look at every link and pin. Look at every bolt boss on the cases/cylinder/head that have any of the timing chain components bolted to them, check them for cracks. Sometimes they just break and other times a previous owner may have installed too long of a bolt into a blind hole.

[Apeterson26]

I will have to pull the clutch off and look tomorrow when I get off work, I am curious what kind of money am I looking at if it were to be the gear on the crank? I can do all the work myself besides the precision work on the crank.

[oldskool83]

the gear looks to bolted to the crank but gears are obsolete.

[Dirtcrasher]

I have never seen even the worst 350X jump time, you have something going on. How are the crank bearings??

The DID chain is fine, it just won't last as long as OEM did but that isn't the issue; if anything I'd blame your cam chain tensioner. I have NOS OEM HONDA 350X/350D timing chains for 90$ shipped.

You are out of luck for tensioner guide and guide, I sold a few sets for 350$ a set and guys were happy to get them. Unfortunately, nothing else fits. I would have never sold them but I still have new take out motors.

Not to mention, the 350X tensioner guide and opposing guide almost never wear out, even in the worst motors I\ve touched they barely seem to wear down. I guess if someone didn't change the oil enough that could be the difference.

I'd change the tensioner, 350X's timing chains do stretch and wear out, but they don't usually jump time. How about your cylinder head journals?? Are they gouged up, is the cam turning smooth or is the chain fighting to turn it?? Backwards oil filters and low oil will ruin those camshaft journals, they it won't turn without allot of effort.