Timing chain By skyrider (Read 540 times)

[skyrider]

Looks like I have a timing chain issue. Last evening I went for a ride through the beautiful mountains north and east of San Diego. After a few miles I turned around to go back to the RV park. Suddenly it started to buck and jump, then it would smooth out only to do it again. After several cycles of that it just quit.
After getting it back "home" I found I could turn the engine backwards with a wrench but if it was turned forward it locked up. Engine never ran hot, oil is fine-just recently changed.
I suppose the next thing is to pull the valve cover and look at the chain from the top.
Any suggestions?
Oh yes, I had noticed that the engine was making more noise that it did before , in fact my wife had just mentioned that it was not as quiet as it used to be. Had been unable to pinpoint the noise, Now we know what it was.

[richardthescooter3]

To me it sound like you may need to adjust the air/fuel mixture ratio screw, (describe this bucking and jumping) If your talking the sprocket area, when adjusting valves, turning the sprocket to TDC it will stop, but with some effort it will continue to turn. Did you check your oil after this happened? Have you check all the vacuum lines and intake to make sure they are tight? Give us some info. What kind of scoot, year, miles, last valve adjustment?

[skyrider]

Sorry, I forgot to give more info. 2011 YY250T 10600 miles, oil is fine and full, just very recently changed. coolant full, didn't get hot. Spark plug color good. CFMoto engine.
I'm almost certain it is a timing chain failure probably caused by tensioner failure. I'll pull the valve cover tomorrow or Tuesday and report what I find.
Valves were adjusted approx. 500 miles ago.

[rcq78]

if you have a vacuum leak,you fuel pump might have quit working......they run in vacuum....

[skyrider]

Something in the lower end let go that causes it to lock up. I pulled the valve cover and the cam and chain are OK. It will crank two or three rounds and then lock up. I turned the engine backwards with a wrench and it frees up only to lock up again. Since we are full time RVers and move to a different place every week it will be hard to tear down and wait for parts. Can't haul it unless it is assembled. Maybe I should just look for a good used Honda Reflex so it would fit my carrier. Also what ever it is keeps the engine from trying to start, it has always started instantly.

[skyrider]

Looks like the flywheel spun on the crankshaft.