Ok, I need to finalize everything for my rebuild.

[plkmonster2]

Ok, here it goes. I'm getting a Ross piston, 85mm, 10.5:1 CR. Ok, and I was thinking of getting rid of the base gasket, but after using the calculator, and reading a bunch of posts, this will raise my compression to 10.8:1. I can only get 92 octane gas, unless I buy R-Tech race fuel 110 octane for like 5 bucks a gallon. I really don't want to use race gas. I run at 1000-0 elevation, and 50-90 degree weather. The humidity can also be at almost 1% all day so i am worried, and don't want to raise it up any more. Is getting the .040 deck clearance necessary in my case? I will be running a HRC cam and HMF pipe with a UNI with all this. I will be running xr gaskets with this, so i will get 10.5:1, I just don't want to use race gas. Should I use a gasket or not on the base? I know cals has got a 11:1 piston with no gasket on 92 octane,with no problems, but I read that some people with just 11:1 have had theirs' ping. Also, could I use no base, but use a ex top gasket to get the proper squish? Say if gasket set a had 2 gaskets. Each was .020. ok, so you have .020 on top and bottom. on kit b, you have 1 top one that is .038, adn .002 for hondabond. Do you get the same squish and same compression?

Also, what tool do you use to file the rings for the piston? Thanks!

[TC426EX]

Theres a special tool for filing the rings, but if you HAVE to, a file will work. The one thing you need to make sure, is that you ONLY file in the direction INTO the piston, and not back and forth or toward the outside...

As far as running 92 octane, in theory you should most likely be fine, but you wont know until you run it at your elevation and conditions. You could always run a 50/50 mix race gas/premium pump if you find you have a problem + it shouldnt cost you too much more for a couple gallons.

I also wouldnt worry about the extra .3 youll get from omitting a gasket here or there, and just use them both. Youre not trying to squeeze every bit of compression possible out of your bike it seems, just build a solid running midrange engine, so the difference wouldnt be significant to you. Using the XR gasket kit alone will help you out, so just do that. Im sure there are some people who run no base gasket, but its not personally something Id try....

[K_Fulk]

A 85 mm piston is the stock bore. Have you taken your motor apart yet to se if the bore is still in spec? Being a 99 i would be surprised if it was.

I agree with Tc on the baskets. I wouldnt do it unless you were doing a race motor. If you do want to bump the compression up a hair I would get the cylinder decked.

[44oEX]

don't worry about the compression, you can safely run 11:1 with pump gas, some people even run 12:1 with no problem.

[400exrider707]

Originally posted by 44oEX
don't worry about the compression, you can safely run 11:1 with pump gas, some people even run 12:1 with no problem.

I've talked to a few YFZ owners running something like 13:1 on pump:eek2: Not something I personally would try, but they claim to have no problems.

[wilkin250r]

Getting the proper squish clearance will actually REDUCE detonation, even though you will get a small increase in compression.

The whole purpose of the squish band is because the head is cooler than the rest of the combustion chamber. Having a squish clearance of 0.040 "squishes" the fuel in between the head and piston, and removes the heat from the fuel in that area, thus reducing the potential for detonation. This is why some engines can run really high compression on pump gas without detonation.

[plkmonster2]

I know everything is still in spec. Yes, it may be a 99, but I still have the stock tires, with 60% of the tread left. This bike has very low hours for its year. It isn't used much, maybe once or twice a week, but only for an hourOn vacation, I may put 4-5 hours on a day, but total, the bike can't get much more than a 100 or two hours a year. It stil runs strong, with no smoke. I just want some overall more power for hillclimbs and such.

[plkmonster2]

Does anyone know the range of the spec? I really need a service manual. Anyone got one for sale?

[K_Fulk]

Inside diameter 85 - 85.010 mm
out of round .05 mm
taper .05 mm
warpage .10 mm

[F-16Guy]

Originally posted by 400exrider707
I've talked to a few YFZ owners running something like 13:1 on pump:eek2: Not something I personally would try, but they claim to have no problems.
Having a water cooled engine will allow you to run higher compression.

[cals400ex]

i run a thin cosmetic flex steel head gasket and no base gasket. i run a 11:1 ross piston and i use pump gas. i do have my piston thermal coated so i don't know if that makes a difference or not. yes, reducing the squish is good. you could probably raise the compression by reducing the squish and run the same fuel as if you went with a thicker gasket. the thing is it will be a bit more efficient with the smaller squish area. also, a cam may play a pretty big role in what fuel you need to run. an aggressive cam with a lot of overlap will require lower octane fuel than a stock cam due to when the intake valves close. for example, on a 450r with the stock cam, you very well may have problems on pump fuel with a 12:1 piston. by adding a HRC cam, you can run 13:1 safely on pump.

[400exredrider]

yeah i run hondabond on the base gasket,,,, with the cometic flex steel head gasket and it works well with the 10.8:1 piston, puts it around 11:1