[thesmith87250r]

Hi everybody, need some help .I bought a basket case trike just for the motor and this is what I was told was done to it. it's a 85 250r trike motor with 4mm stroke ,decked cyl. ,port n polish,shaved head. well I put the motor in my 87 r threw a compression gauge on it cold and wide open on the carb getting 230lbs of compression. which is more than I expected this bitch is stout. don't wanna fire it yet knowing it will probably need race fuel. I wanna get her back to 180 -200 . I was gonna put a stock head and 3 piece gasket on it was wondering if anyone has something similar to compare and where to start jetting with a stock carb. and if its possible to lose that much compession with that change is what Im really interested in. thanks for any help.

 

[american opel]

most likely you are going to have to run race fuel no matter what you do.to me I wouldn't even think about running pump gas anyway's,even with a stock motor.it just isn't worth the hassel.you might be able to have a head cut,and a different head gasket but that's something that a builder would have to help you with.

 

[C-Leigh Racing]

Man!, 230 lbs compression, sounds like my kind of engine, a grunt & go type.
By you asking about adding the three piece type head gasket, are you saying it only has the real thin head gasket on it now ?.
If it only has the real thin one, by removing it & then using the three piece type head gasket, yes it will reduce the compression some, but probably only around 15~20 lbs. If still around 200 lbs, you could probably get by with a 50/50 mix of 110 race & 93 pump, but you'll need to really be on top of jetting, keep that carb rich the combat the compression heat.
I would say try the three piece & see where the compression stops at, but if thats not where your wanting it, best thing would be another head & have it machined properly or either a cool head with the right cc dome.
Neil

 

[acecarlos]

Hi everybody, need some help .I bought a basket case trike just for the motor and this is what told was done to it. it's a 85 250r trike motor with 4mm stroke ,decked cyl. ,port n polish,shaved head. well I put the motor in my 87 r threw a compression gauge on it cold and wide open on the carb getting 230lbs of compression. which is more than I expected this bitch is stout. don't wanna fire it yet knowing it will probably need race fuel. I wanna get her back to 180 -200 . I was gonna put a stock head and 3 piece gasket on it was wondering if anyone has something similar to compare and where to start jetting with a stock carb. and if its possible to lose that much compession with that change is what Im really interested in. thanks for any help.

Carefull with putting a stock head on. Most likely the current head has been cut to accept the plus 4 MM stroke. As Neal stated, If currently you are using the thin .0098" OEM metal gasket, go to the OEM 3 piece metal gasket, you can also add am extra thin OEM metal .0098" gasket to the stack as a poor mans way to reduce compression.

Carlos

 

[thesmith87250r]

thanks for the responses I got a 3 piece gasket from a friend . and when I get it apart I will check the head . I will also shoot some pics. I'm working now and will get at it later and report compression change. thanks rich

 

[thesmith87250r]

It dropped down to 210 lbs with the 3piece gasket and my coolhead that had a bigger dome. The piston is 67.5 from what I can make out and the gasket was not a cr gasket but was graphite and thick but not as thick as stock. So any help on a mix and jetting on stock carb would help. I did try to fire it up and it kicks back like a mother humper.with 93 at 32 to 1 with hp2.

 

[bigred]

210 still need race gas man. What cc is ur cool head dome usually says on the side of them

 

[thesmith87250r]

Nothing on the side of the head for dome cc

 

[american opel]

you are asking for trouble running that much compression and pump gas.if the cool head has a removable dome,you have to pop it out and the cc will be on the backside."i think".

 

[C-Leigh Racing]

So, the head you are using is a Pro Design cool head ?.
What really needs to be done, is the dome machined again, the bowl area cut some more to reduce compression.
Only thing about that, if the dome has been machined so that the piston can run up into it for the extra stroke, the dome itself is mighty thin now & by machining on it some more, could be cut through into the coolant jacket. Cool head domes, have a fin like surface on the outside of the dome & if the bowl area is cut on to much, could dig down & open up in the low part of those fins.

Cheapest way out, would be stack the gaskets like Carlos mentioned, not the best way to go about it, but its that way or spend a bit of money to get it fixed by machining the dome.
Being the Mcguyiver type person that I am, I would stack the gaskets & let that baby roll.
Neil

 

[thesmith87250r]

yes it is a pro design cool head . it has what looks like a bigger spacer plate than my buddys 89, so the head wasn't machined to except the stroke. I'm gonna grab some 110 on Monday and give it a try. the biggest main jet I have is a 178 I think . we will see what's gonna happens. does anybody know if the o rings for the petcock are some thing I can match up at a parts store ,I forgot I had a leak last night got to fix that before I try to run the bike.

 

[acecarlos]

Yes, the petcock simple round o-rings can be matched, it is a metric size. The 'x-cross' o-ring can not as it is a custom Honda OEM product.

Carlos

 

[KASEY]

what about throwing an extra base gasket in also? I know it raises the ports but not by too much,,,

 

[thesmith87250r]

well I priced some 110 and it was 80$ for 5 gallons . so I got another 3 piece gasket and that put my compression right at 180. so it's gonna have to work for now until I figure out how to mill the dome in one of the spare heads I have any help on that would be appreciated , im gonna do some research on that If I can find any. I have access to a machine shop, but if any of ya eng. builder want to shoot me a pm on a price to do it would be helpful. thanks

 

[acecarlos]

While you are at It, check your UCCR. Look under the BDTM section in this forum for a full explanation on UCCR, it is rather simple process, and will tell you the CC's you need your dome to be for the fuel you are running.

Carlos