My question:

I want a 426 piston but JE doesn't make that size, so I am left with wiseco. They have a 10:1 or 11, I won't run the 11:1 because of race gas. I ride only in dunes so I need the most quickness of power. Should I get a 426 10:1, or 416 10:8:1. I need help, which would have the most power, and which would be the fastest in a drag race.

 

Are you sure that you have to use race gas with a 11:1 piston. I know that Gt Thunder says you can use premium pump gas with their 11:1. Are you happy with the pieces you have gotten from Gt? I am considering having them do my 440 kit. I plan on using the 11:1 and I know I dont plan on using race gas.

 

Ive always heard to use race gas with anything over 10.25:1 Compression pistons

 

I am ordering the GT stuff in November. There 400EX's they build are the top of the line. They raced a full race 440EX built by one of the top engine builders, and there 440 beat it 20-30 feet per gear. There're awesome. But I still need help on the piston Question.

 

Your topic got me to thinking. So last night I e-mailed Lazarus Sommers at GT Thunder and asked a few questions about 440 kits. I received his reply today. He said 11:1 with premium pump gas was "no problem". He answered all my ?'s and was very helpful. I suggest you e-mail him with yours. I knew that they had alot of experience with 400's but I did not know that they were that good. I guess I am lucky that his shop is only an hour or so from my house. I am pumped to have him install a 440 kit on my bike. Now if I could just figure how to pay for it!

 

Hello fellas
Look at it ths way i can ride all day 6 to 7 hours and use maybe 3/4 tank of gas it wont be that expensive to run race gas ....

 

Yes, JE does make a 3mm over (426cc) piston. Their standard, off the shelf piston in that size is somewhere over 11:1. I do have a catalog & can get you part numbers if you like, but it will probably be Monday or so, since I am leaving for the dunes this afternoon.... Also keep in mind that JE can make any piston you like to any specifications.

I would tend to think that the 10.8:1 416 piston would develop more power than a 10:1 426, as additional compression would more than likely substantially outweigh the negligible increase in cc's, though I don't have any dyno stats to back me up.

I would also be concerned about the 3mm over (426) piston in the stock sleeve. My sleeve was getting on the edge of too thin at 2mm over (416cc). I would not personally go any farther without re-sleeving up to the 4mm over (435cc).

Personally I have the 10.8:1 87mm (416cc) piston, and XR400 camshaft in my bike. I think it would run fine on 92~93 pump gas, but have personally decided to run a blend of pump and race fuel, just to be on the safe side. But, again, if I didn't have any race gas available, I think I would be fine on premium.

 

tell me how good the 416 works out. I would think that the 416 is a lot quicker, than the 426. Just reply when you get back.

 

LRd, as long as you have a bigger cam, you shouldn't have to run race gas. I have a 11:1 Ross piston with an XR400 head gasket in my 400EX. My comp. ratio is approximatly 11.25:1 and all i've been running is premium pump gas(92 octane) and adding some octane booster to each tankful. I have the Web-Cam and Lectron carb on my bike also, along with a DMC double barrel exhaust. I have never heard any predetonation running pump gas, and i have tried using race gas, and it made no difference on my bike. I, myself would go with the higher comp. piston. More comp. really makes these motors go. My next set-up is going to be a 416(13:1) piston and a full race cam. Then it's bye, bye Raptor.

 

My friend just had the 426 kit done with 13:1 . It was funnyinh seeing him ride it the first time. He has stock seat cover. Every time he hit the gas he would allmost fly off the back.