timing jumps By bigrustysr (Read 1,128 times)

[bigrustysr]

i have a twister z150r go cart (gy6 engine) keeps jumping timing--replaced tensioner-no help- will run 5-30min then jumps again chain looks ok of course cant tell if streched==tensioner is all the way down cant tell if gear on crank is ok but from what i can tell looks ok --help please--ps is varator nut turn clockwise to remove or counter clockwise.

[cyborg]

my money is on a stretched chain,,,how many hours on the engine?

[jct842]

One thing I know from experience there are some engines that will jump time if you rotate the engine backwards/ The chain tensioner acts on a strip that rides on the chain. That may be worn also.

RIGHTY TIGHTY.....LEFTY LOOSEY Use an impact if you do not want to damage it. Fingers can hold it while impact take off the nut.

[bigrustysr]

cyborg- cant even guess how many hours -but has a bunch can you get new chain on bottom gear thru varactor-clutch side dont want to do complete tear down

[Bashan]

Alley has a post on that, let me go see if I can find it....I'll be back.

Here you go, Alley's sneaky cam chain installation.

[Alleyoop]

The sneaky chain replacement only works on the 250s the case hole is big enough for the chain to go in but not on the 150s.

Concerning getting out of time I do not believe it's the chain for it to jump teeth it has to be really loose. I think its the WOODRUFF key that holds the FLYWHEEL in position on the crank. It is probably sheared off and that is why the timing lasts only a few minutes. As you crank on the throttle after re-timing it the flywheel is rotating on the crank and your out of timing again.
Alleyoop

[cyborg]

AAAH the guru speaks and i think he's right once again!!!

[bigrustysr]

got to buy me a impact wrench tomorrow-to get varactor nut off -i need one anyway -will check woodruff key then chain is proably the answer new tensioner extends all the way down

[tvnacman]

See if there is play in the flywheel to crank shaft . The woodruff key could be sheared .

John

[bigrustysr]

no play in fly wheel jumps off gear on crank-tensioner is going all the way down to its limit--just did top end rebuild -new head complete with every thing-new cylinder,piston and rings ran great for 2 days then started this jumping timing

[jct842]

Check height of new head verses old head. It is possible that the chain is jumping because of incorrect slack for the tensioner to work with.

[Alleyoop]

Jun 23, 2014 10:35:45 GMT -6 bigrustysr said:

no play in fly wheel jumps off gear on crank-tensioner is going all the way down to its limit--just did top end rebuild -new head complete with every thing-new cylinder,piston and rings ran great for 2 days then started this jumping timing

Now we find out you replaced the top end, and that could cause the chain to jump if the head or jug are shorter in height from the original.
Alleyoop

[bigrustysr]

slight over sight on my part lol checked height on head and jug both the same as original close as i can tell with tape measure

[bigrustysr]

how can i take a link out of timing chain with it still around crank shaft-do they make a master link for timing chain i can get link out but getting it back together will be hard trying to brad it back

[bigrustysr]

must have bad breath--- no one responding