Question on Hi Comp Piston

[xtreme762]

I wonder if there is a way other than tearing the motor down, to tell if it has a Hi Comp. piston already in it?

The reason I ask, is because I put 93 octane gas with 3 oz. of Lucas octane booster in the tank. I had 87 octane in it with Seafoam to clean out the combustion chamber a bit. Well, it's a night and day difference between the two fuels. I mean this thing runs noticeably WAYYY better with the 93 octane mixture in it.

I also noticed that before I changed the fuel out of the tank. I had a very small "Ping" when the motor got to operating temp. and was at a high RPM. The "Ping" wasn't real bad or even real noticeable. Not bad enough to cause a problem.

So, I'm thinking that the guy that owned it before me already put a Hi Comp. piston in it. He had Laeger A-Arms installed, and a rear caliper block off plate on it. So it obviously had been modified.

Without tearing it down, is there a way to tell if it already has a Hi Comp. piston? I'm new to the 400EX scene. So I don't know if there may be a trick to find out or not.

[Pittsburgh400ex]

I'm not a mechanic and dont know stock compression numbers but if you di could just do a comp. test yea?
I tell a difference between 87 and 93 on mine and it's just 11:1 if that tells you anything.

[xtreme762]

Why I didn't think of that is beyond me! Great idea.

Mods, if you want, you can delete this.

Thanks

[Pittsburgh400ex]

Originally posted by xtreme762
Why I didn't think of that is beyond me! Great idea.


Every few years i get a good one, lol.

[powerbomb400]

First thing even with the stock piston it is recommended to run at least a 91 octane fuel. I myself run a mixture of 110 leaded race gas with 93 octane unleaded w/no ethanol. Alot on here run 93 octane unleaded pump gas. Unless it is a 11.5 compression or above it should run fine with that. Try to if all possible to run without ethanol. I have my own personal reason to run the mixture I do and it is available where I live for about the same cost as regular unleaded fuels.

[xtreme762]

I've looked around and can't find anything better than 93 in my area without spending an entire paycheck on 5 gallons. So, I'm stuck with 93 and octane booster(Lucas). I'm thinking if I mix it 2:1(2oz. to 1 gallon), it's probably around 93.5 - 94 octane at best.

When I got the bike. It had 105 octane in it, which is another reason to believe it has a Hi Comp. piston in it. I can't check the compression until the end of the week as I loaned my tool out and haven't gotten it back yet.

With the 93 and Lucas octane booster, it runs about the same as it did with 105.

[Pittsburgh400ex]

i normally mix it 50/50 turbo blue and pump 93. It;s overkill i know but i destroyed a 12.5:1 quickly not running correct fuel. It runs on 93 fine when i have run out of the mix but i guess just a little piece of mind for me. Turbo is around 8$ a gallon n my area.
If he was running 105 and your positive on that i'd almsot bet on it being over 12:1. 110 is recomennded for 12.5:1 JE from sparks, my old setup.
If you do find out what the comp ratio is and it's a bit high for the price of fuel can slap and extra head gasket in there on lower it a tad. It's done on my 450, previous owner decked the head.

[powerbomb400]

If there is dirt track shop anywhere around they should have race fuel. I give 7.00 dollars a gallon for 110 leaded race gas. One reason I run the leaded gas cause I bush hog with a 1949 8n Ford tractor. When it was made 100 octane leaded fuel was the lowest you could get. In runs a heck of alot better with leaded fuel than unleaded fuel.

[Pittsburgh400ex]

Originally posted by powerbomb400
If there is dirt track shop anywhere around they should have race fuel.

That's exactly where i buy mine. They can also order you virtually any octane gas you'd want to run for your motor, anything from 87 crap to 120+ I certainly don't need anythnig that specific but if you can get a 105 (what you said it ran good on) and it's cheaper than what they stock, go for it. Another option is AV fuel. Not sure on the octane of it but the price is quite a bit less than race fuel. Private airport is 20 minutes from my house, same as the speed shop but not everyone lives close to those buisnesses.

[cooterwrenchen]

Originally posted by powerbomb400
I have my own personal reason to run the mixture I do and it is available where I live for about the same cost as regular unleaded fuels.

what last time i went to get some 110 here in nor cal it was around 10 F*^&%#* a gallon:eek2: your lucky

[CJM]

100LL 100 octane low lead av gas. Buy it at the local small airport near ya.

[xtreme762]

I haven't checked the air port yet, but for 110 at the track they want nearly $9/gallon. I'm tryin to locate some 105 and use some toluene or something else to make it higher. If I can get the toluene cheap enough.

Haven't located 105 as of yet.

[400exwhipper]

What kind of fuel would I ask for if I went to an airport?

[powerbomb400]

Buy 2 or 3 gallons of 110 leaded and 2 or 3 gallon of super unleaded and mix them together. That's what I do and it will work just fine. Super is already 4.00 a gallon here now.

[xtreme762]

What year did Honda start coating the cylinder sleeves with a thin coat of nikasil?

I called my local machine shop and he quoted me a price of $270 to bore this jug over .040" if it is coated, and $90 if it isn't. The $270 is so high because they have to take the coating off, bore it, and then re-coat it.

I'm hoping they started around the 2005 time frame when they made the most changes to the bike.

Anyone know?

[CJM]

No 400ex sleeve is nikasil coated.

[xtreme762]

Originally posted by CJM
No 400ex sleeve is nikasil coated.

I didn't think so, but the guy I spoke to seemed to think they were. He must think the cylinders in the crotch rockets are the same as the ATV's or something.

Thanks, CJM

[CJM]

Your welcome.

[powerbomb400]

Suzuki coats their jugs. We took my dirtbike jug and put a sleeve in it instead of the coating.

[Stickman400]

The 450R has it too, I'm sure there are alot of others.

[Crosshairs]

Originally posted by CJM
100LL 100 octane low lead av gas. Buy it at the local small airport near ya.
Where do you buy it ..My local airport wont sell it anymore....

You can PM me if you dont want to post it..:)

[powerbomb400]

You can't slowly drive in. You have to fly in to the parking lot.
:D

[CJM]

Lakewood airport will sell it to you.

Why wont they sell you gas at your local airport

[Crosshairs]

Originally posted by CJM
Lakewood airport will sell it to you.

Why wont they sell you gas at your local airport
I went to Allaire and they said they only dispense it into aircraft.......weird cause I used to buy it there years ago.....
Ill try Lakewood...

Thanks