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Can using two head gaskets reduce pinging on 2 stroke?

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First off, yes, I'm talking about a two-stroke here, namely a CR250. It has been bored 2mm over, ported, and received a carb job. Problem is that I can't get rid of the pinging without race gas or octane boosters. Frankly, I'm no longer in the mood to pay extra $$$ to ride the bike. I'm tempted to try two head gaskets to see if reducing the compression will get rid of the pinging.

I was thinking of either two standard thickness gaskets or one standard and one thinner high compression gaskets. I've looked for the thicker gaskets from Cometic been noone I've checked with carries them.

Anyone have any working experience with an idea like this?

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I believe that you can buy a thicker base gasket and head gasket. I wouldn't stack two gaskets on top of eachother, you might have sealing problems. Those CR's are hard to get to seal as it is.

Oh, I just thought of an easier fix. Pull you ignition cover off and retard the timing a few degrees and see if it helps. You'll lose a little bottom end, but not much.

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Using 2 base gaskets will change the port timing & not what you want to do. You can call cometic 1 800 752 9850 they sell direct & probably have what you are looking for.

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Mix the race gas half and half withe pump gas. I know how u feel i went through the same thing but the bike requires to not ping about an octane rating of 98. Not using the correct octane wears heavily at your rings

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Thanks for the repsonses. I checked Cometic's and Wiseco's web site before for thicker gaskets but without luck. I'll try calling them about "custom" gaskets. If this doesn't get rid off the ping after further jetting the bike goes up the river or gets a stock jug.

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Oh, I just thought of something else. Why is this in the jetting forum? :D

Because pinging is often associated with jetting so those with jetting experience would be more likely to have experimented with other idea to reduce ping. That and the fact that there is no 2 stroke forum here :D That's a shame because this board is tops bar none for knowledgable responses.

BTW--good point about the head gaskets and sealing.

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What jetting changes have you tried? Does it ping only in the summer when it's hot but run good in cooler temps? Pinging is usually a sign that it's lean. You can try rasing the needle a clip or two(lowering the clip on the needle rases the needle) You can try going up on the main jet & pilot jet. Where is your jetting at know, Main, pilot, clip position, air screw & what year is it?

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Because pinging is often associated with jetting so those with jetting experience would be more likely to have experimented with other idea to reduce ping. That and the fact that there is no 2 stroke forum here :D That's a shame because this board is tops bar none for knowledgable responses.

BTW--good point about the head gaskets and sealing.

Yeah, I guess that I'd be hard pressed to find a better forum for it. Sorry. :D

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Who did your motor work? Was the head modified? Get ahold of Eric Gorr at Forward Motion, he's done all my mods in the past and does excellent work. When you get a port job done they'll ask if you want the head modified for pump or race gas.

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Actually, Eric Gorr was the one that did the work. I spoke to him about a year ago when I got the bike and he gave me some settings but it's still no good without high octane. I was thinking he would be the guy since he did the work AND is only 6 hours away so the altitude and climate are nearly identical but, oh well...

Right now the closest I've gotten is with a 35 pilot jet (stock 30) and second clip in the needle (optional needle per Eric's recommendation). If I engage the choke it runs horribly--big time bog and almost dies everywhere in the throttle range. It's also leaving my fender black so try as I may to think that it's pinging from being lean I just don't think it's lean (it also doesn't surge or fall off like it's lean). It's usually pinging around 1/2 throttle so I suppose I could try the clip again together with the 10 degree temp drop and see if it's closer that way.

The thing is though that I've been chasing this problem since I've had the bike (1 year) and never get rid of the ping without a liberal amount of octane boost or $$$$ gas. Anyone have a stock cylinder jug for an 01 CR250 they want to give away?

REDBEARD--no need to apologize. Technically I probably shouldn't be asking 2 stroke questions in thumperland but, like I said, the help here is prime.

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It can be lean enough to cause it to ping but not enough to cause a surge. When it's slightly lean the cylinder pressures go way up & with high ambient temps it makes it worse. If the engine was jetted for race fuel & then switched to pump fuel it will be lean. I wouldn't give up on the cyl, I would spend some time trying jet it. I would start with rasing the needle.

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adding another base gasket will only change port timing .015".you will never notice it.it will cure your ping and you can get on with your life.

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So lowering the compression is how you fix a ping? So when I got my new cr250 & it was pinging I should have ran down to the honda store & pick up another base gasket? Or should I have spent some time changing the jetting? Maybe you could give him some advice on what to change to try help the problem not just making him go away. It may be that the engine has too much compression for pump gas but he should try jetting first.

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he has tried jetting it out.the motor is not stock,it does have too much compression for pump gas.he already has it so rich its puking all over self.

stock motor is a completely different deal.but yes,if a stocker was pinging i would either use better fuel or lower the compression rather than riding it slobbering rich.

i highly suggest you calm down a little.the is a discussion forum.we can do so with out bashing.

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he has tried jetting it out.the motor is not stock,it does have too much compression for pump gas.he already has it so rich its puking all over self....

You got that right :D Right now to eliminate the ping even with octane booster it's running a 440 main jet. When I spoke directly to Eric Gorr he said that I should be using 400 or 410, assuming race gas. The 410 is stock but he said that that was likely too rich. I've got 440 main, 30 pilot, 2nd clip on the needle, and 1 1/2 turns out on the air screw. This runs OK. A 35 pilot creates a massive sputter with the clip in the second slot and it's still groggy in the first slot; a 30 pilot is alright with the clip dropped in the second slot but it's still not great.

I'll try again to call Cometic tomorrow during business hours and see what happens. If that's a no go I'll have to wait til the end of the week to try doubling the gasket. Another thought, what IF Cometic could get me a custom thickness base and jug gasket? Would splitting the difference be better or not really worth the effort?

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either way is fine.

getting your jetting back to where its clean will negate any loss of compression or slightly altered port timing.

440 main jet is definately to rich.

you will get it handled.just on a side note,have you ever checked the cranking compression?

it has to be 200+psi.

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