cfmoto 250cc jumped time

[kingster]

I bought a used hammerhead 2500ss and the guy said that the engine has jumped time. so how can I fix this and what parts do I need?




thanks in advance

[Masteryota]

Um, well first you need to find the culprit that caused it to jump, otherwise, all repairs may be done in vain.

If the engine is an 'interference' engine, you need to take the head off and examine the valves and piston closely. Any impact on the valves means they need to be replaced. Chuck the valves in a drill motor and spin, any deflection, and they are toast. Depending on the nature of the damage to the top of the piston, it may also need replaced. Check everything connected to the valves, springs, retainers, guides, seats and rockers for damage. After that, you will for sure need a new chain, possible guides and cam sprocket, and get a new tensioner as well.

FYI, this still applies even if it is not an interference engine. I have seen plenty of non-interference engines touch valves to piston when a belt jumps at high RPM.

[kingster]

I think the guy said something about the pistons and the valves

[Masteryota]

Then I would plan on doing some moderate internal work at a minimum. Most of it is pretty easy, except the timing chain replacement. You might be able to get by without it, but I would not risk it.

Like I said, all the work aside, need to find out why/how it happened, then repair from there. I would start looking at the tensioner and guides.

[kingster]

ok and if I replace the pistons I might as well install the 300cc big bore kit while im at or just get the stock piston

[Masteryota]

Should only be one piston, unless there is another CN/CF250 design out there. The BBK depends on your overall budget, but I say go for it!

Have the head reworked and matching cam, and build a monster.

[Insert Tim Taylor Laugh]

[kingster]

I guess you mean a port and polish with the head rework.. how do i do cam matching

[Masteryota]

Well, I used the wrong term, but you would need a cam that 'matches' your driving needs. Low end, top end, mid range, etc...

[kingster]

so how hard do you think it would be for a non professional person to install the timing chain and valves tensioner and guides? how long do you think it would take?

[351mustanger]

Originally Posted by kingster

ok and if I replace the pistons I might as well install the 300cc big bore kit while im at or just get the stock piston

Get the piston that fits. Meaning: measure it before you buy it, unless you are replacing the cylinder at the same time. You never know, it could already have a 300cc kit on it.

[kingster]

ok cool but do you think I could replace the timing chain as a non professional