98 XR600 in storage for 3 years

Working on a 1998 XR600 that has been sitting for 3 years. Cleaned the tank, Carb, and added new gas. Shot a little oil in the cylinder for compression. I pulled the plug and noticed that the plug gap was closed. I put a new plug in, and started the bike. The bike started after a few kicks, but started missing badly. When I removed the plug again I noticed that the gap was near closed again... Seems that the piston is tapping the end of the plug. any ideas..... The new plug came from the honda shop and was listed for the bike............ I can purchase the bike for 700.00, and the bike is in great shape.. I just was not sure about the plug gap... Thanks

Sounds like you have a piston pin, or bottom end bearing problem. Excessive play in either or both areas might lead to the piston hitting the plug.

Or, is the plug the correct one? I'm not sure if they ever used any long throw plugs on other bikes. There may be a mix up.

The correct gap is the typical .030 or .7mm to .8mm. The correct plug is a DPR8EA. The P stands for "projected electrode." It basically sticks out a little further into the combustion chamber. The R is for resistor. A R plug is not really necessary. A non projected non resistor version, the D8EA will work too. The D8EA is used by a lot of bikes so it should be easily available. Perhaps try one of those and see if you can get it to run a little longer so you can see if it is making weird noises. If it is the crank or rod bearings it should be quite noticeable.

Seems like a kind of a bizarre symptom. Could a high compression piston be to blame? My other weird thought about it is maybe it was bored to 100mm and a XL600 piston was used. The XL piston had a larger piston top to wrist pin spacing. Perhaps this is why it sat for three years. Maybe put together without base or cylinder head gaskets? Cylinder/head decked (resurfaced) too much?

I would guess a poor mans high compression mod. They have the head shaved and took too much off the head.

If you can find them a head shim gasket could solve the problem. If the bike is in as good as shape as you say it would still be worth it to get it and do some engine work.


where in ohio are you located

Im located in gallia county,, Ill try the D8EA, and I will also check the gaskets, and see if I can tell if there has been any other work done to the bike. I think I will purchase the bike, due to conditon it is in, maybe deal on it a little more anyhow....Thanks for the help,,, Ill let You know what I find out....

I guess when you cleaned the carb you would have noticed if the choke flapper was broken? They sometimes break off and get sucked in the engine. :thumbsup:

The choke flapper was in tact. I tried a new plug (D8EA) and I added another washer...... I started the bike today,,, It ran great, I put around 8 miles on it, and it seemed fine. I could only guess that at one time someone has shaved the head on the bike, but I cant tell that any work has been done to the bike...... Thanks for all Your help....

Post some pics of the head you can normally tell if there has ever been a wrench on the head bolts

Seems weird for a piston to reach that far into the combustion chamber as to actually contact the plug electrode. I mean, I've heard of domed pistons, but that is crazy. I figured it was the plug being too long, good job man! Enjoy the bike! :thumbsup:

Could a large amount of carbon build up on the piston do this?

could it be that the head has been shaved? in the past - a wee bit too much or a wrong head gasket installed - or none at all? or crushed badly? try a shorter reach plug by a thread or two of the same heat range. If the bottom end was bad it owuld of been one NOISY SOB when it did run and there was no mentionof that.

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