Time to rebuild the Banshee top end.I was going to use the hi-po kit from wiseco but sever friends got them and have to run race gas.We have to drive about 30 minutes just to get it so I'd rather not usse it if I can help the power in other ways.

I'm thinking of useing the regular wiseco pistons and adding a P-D cool head.From what I've seen the 22 cc domes are the same as stock comp. so they should be fine on pump gas,wondering how low I can go without race gas/octane boost????

Anybody using the cool-head with 21's or 20's on pump gas???

Greg

 

i have the cool head on my banshee and i got 2 over stock size i believe they are 21 or 22 and i run my banshee on pump gas i put 92 or 93 octane in it and it runs fine


joe mod banshee

 

I agree. I just had a few thousands taken off the stock head for the extra bump. Pretty cheap too.

 

If you call up Alba Yamaha they have decked heads for 85 bucks. I think you can get either 20 or 21 cc heads. It sure beats spending 240 for a cool head.

 

Thanks for the help. I order a cool head with both 22 and 21 cc domes today.Pro-design will only guarantee the 22 (which barely up the cmpression) to work with pump gas.I'll try the 21's too with the hope that with my altitude and maybe a mix light on race gas heavy on pump gas will keep it from knocking.

I didn't want to shave the head due to temp concerns,with the kind of riding we do it's already puking coolant more than I'd like so I'll take all the x-tra cooling I can get.

As far as 18 cc on pump gas...there's gotta be more done somewhere a bike exactly like mine(same mods/year) detonated with the wiseco hi-po pistons and they only up the compression 12 lbs...

Greg

 

I would not have thought it possible If I hadn't had the experiance myself.The bike was not lean we actually chased what we described as a noise in the bottom end tried diff jetting and plugs ran a nice tan color......till we had it out for a whole day......completely destroyed the end of the plug....so we started checking with the shop that did the rebuild...They had used the wiseco hi-po piston kit instead of the wiseco stock replacements...without telling the owner....switched to race fuel at the shops suggestion and the noise went away...no more bad plugs and jetting is fine....

These are not the regular wiseco oversize pistons they are hi compression pistons,similar to (if not the same as) the one sold by VITO's and Majic.The adds say around 12 #'s never checked to be sure.

As far as cooling goes anything is better than doing something that makes the temps go up.we do alot of wide open hill runs at fairly low speeds this makes for real hot motors,any any of the bikes we ride and i don't want to anything that might raise that temp further.Even if the cool head is onlly the same as stock it's better than more heat from shaving the head.

Let me give you my definiton of detonation or pre-ignition maybe I'm useing the wrong term.but when compression is or cyl. temps or combustability(?) of fuel is raised high enough the mix will detonate before TDC or before the plug is fired(usually a little BTDC anyway).

I had never seen this in a 2 stroke untill the above mentioned quad.We actually tore the tranny down looking for a chipped gear that might be causing the noise.Sounded more like it was in the trannie than the cyl. but the high octane fuel solved the problem....

 

i have 17cc domes and i run super unleaded with octane boost and i have no problems..

 

From my experience, the cool head does very little to keep the engine cooler. It seems to keep it cooler toa point, but once all teh liquid has heated up, it gets just as hot as a regular head. I have noticed, that it does cool a little quicker upon resting. As for as compression, 185 seems to be the threshhold for race gas in my experience. 17cc domes usually give somewhere in the neighborhood of 165-180 psi. Allot of it will depend on your porting. Cylinders that have rather large ports will have lower compression. I have a set, and the exhaust and intakes are very high durations. With 16cc domes, I only have about 170lbs of comprsssion! I have never seen an engine pre ignite as you have stated. If the only thing that was done was the pistons, then your compression was no more than a max 140 psi. This is nowhere close to being enough to pre ignite. Pre ignition is caused by the fuel not having enough resistance to reamin stable under the compression hte engine is exerting. The fuel actually fires from the compression and not the spark. This is the ping you here. Detonation, is caused by a lean condition. Personaly, I prefer the stock head, its cheap and works well. I have a coolhead on one of my motors, and it really makes no difference. I guess its what you want though.