Technical Q - two stroke owners/riders

[Pierce]

I've got a Honda CR250R 2005 model. Have a couple of issues I'm unsure of the reason for these things happening.

First thing is:

Engine is pinging quite a bit in certain revs (1/2 to 3/4 revs), not below or above that though. I've tried using octane booster and always run 98 fuel. I know that these bikes are known for the pinging issue but couldn't find anything online about the cause or solution.

Had a feeling it could be jetting but i'm not entirely sure. Have got FMF powercore 2 shorty and FMF gnarly pipe but other than that it's standard running standard jetting.


Second issue is:

It seems to idle really high and mainly when it's warm. It's fine when cold but idles really high and get's higher when warm. Could this be a jetting thing too or just some settings i need to tweak?

I'm not that familiar with how the engines operate as have been riding 4stroke for the past year and haven't had any issues like this.
Any help would be muchly appreciated. Just threw a new piston and ring in today so it'll be nice and fresh.

[dangerous]

tending to think its a bit lean, you could try a bigger main jet, check the needle for condition... Look for a 'air leak' around the carb/manifold, base/head and the exhaust at the header and all welds.

Now if you just pulled a piston out, whats the condition of it, is there pitting on the top? seizure marks?

[Danger]

Yes I've spoken about this bike before. Pinging usually indicates a lean engine condition and or advanced timing. Honda had given up on two strokes by the time these rolled out and never really sorted out the engine on the '05s and up. They deserve scorn for not caring about the two stroke and pumping out the same crap and then dropping them without trying to put them right. Your right they are a jetting nightmare. Seem to be rich and lean at the same time, they ping and yet can foul plugs. People will speak out and say theirs works fine blah blah well fine, use their engines and see how you get on. They can be made to work better, buts its more difficult than most bikes or than it should be. I suspect they need a different needle but the owner I knew with one never really got motivated enough to go that avenue and continued to just tweak with his air screw and change plugs and eventually go KTM.
One thing you can try which seems to help them a little if you have been chasing your tail trying to jet around the issue is to retard the timing slightly.
Pull the rotor cover, undo the bolts and rotate the rotor about a penny width or an 1/8 in the same direction as the rotor turns. This may help a little but is not the full cure. The rest is jetting (other than the motor) and we also found an 8 series plug to work better than the 9 series that Honda spec. But it requires constant tweaking for the conditions to try and optimise this engine.
There have been quite a few jetting threads posted on here this year re the Hondas and other bikes. Try searching or there is a heap of stuff if you google as well.
Here are some threads about jetting on this site, not sure if they apply to your situation but could be worth a read.
http://www.kiwibiker.co.nz/forums/showthread.php?t=64716
http://www.kiwibiker.co.nz/forums/showthread.php?t=65320
http://www.kiwibiker.co.nz/forums/showthread.php?t=70119
http://www.kiwibiker.co.nz/forums/showthread.php?p=1630932#post1630932

[B0000M]

mine does it a bit as well, but has never bothered me enough to do antghing about it. i run a 430 main jet, fmf fatty and shorty exaust.

does it really bad on low octane fuel.

[CookMySock]

Just threw a new piston and ring in today so it'll be nice and fresh.was it pinging before this? This is a water-cooled engine? I bet its leaking water in somewhere.

Steve

[B0000M]

was it pinging before this? This is a water-cooled engine? I bet its leaking water in somewhere.

Steve
na its not water leaking, they all do it - the 05+ seems to do it more than the 03-04.

something you learn to live with, but definately dont ride with low octane fuel. nothing's been damaged from it so far and ive done a lot of hours

[Pierce]

tending to think its a bit lean, you could try a bigger main jet, check the needle for condition... Look for a 'air leak' around the carb/manifold, base/head and the exhaust at the header and all welds.

Now if you just pulled a piston out, whats the condition of it, is there pitting on the top? seizure marks?

apart from a bit of carbonization the piston was fine. I think I will pull the carb downtoday and have a bit of a jam with the settings. MY brother is running an 07 and his doesn't have any of these issues but I believe is running an aftermarket needle and reed block.

[B0000M]

what exaust system are both bikes running?

[Pierce]

what exaust system are both bikes running?

His is pro-circuit platinum with fmf shorty
mine FMF gnarly and fmf shorty

[theblacksmith]

I definately agree with Danger on this one.Pinging or pinking whatever you want to call it is a result of the fuel igniting prematurely or too early.It will still happen even if you go richer on the mixture usually.Retard the ignition timing is the most common answer - has anyone ever looked at the possibility of extra engine cooling somehow, good quality coolants, heat sinks etc? Do these particular engines run quite hot?Other points to look at is compression ratios - heat range of spark plugs etc.
In one way its a shame they did away with leaded fuel I suppose.

[B0000M]

under normal circumstances they dont run excessively hot, definately not as hot as the 4 strokes. retarding the timing would probably get around it.

does anyone know if the TPS sensor on them affects the iginition timing or just for the RC Valve?

its definately not a heat issue as it will do it weather the bike is semi warmed up or completely warmed up.

the only variation ive noticed is on some tanks of fuel its better than others - probably due to fuel inconsistancys