Raise Compression?

[1952]

I need some imput about raising compression, Stock bore & stroke, aggressive dune port,+4timeing, V Force2 reeds, 30mm carbs, Ripps head ,FMF Fatties ,K&N pods. I am running 150 compression. Pump gas. 900Ft El. What would be the pros and cons for raising compression to 180? Thanks Fred

[knight_ripper]

shouldnt you be running 110 octane with your PSI so high? I thought anything over 140 PSI should at least be running 50-50.

 

Also...I hear the more ponies ... the harder shee is to shift. Might not be something to consider. Depending on your riding of course.

[1952]

shouldnt you be running 110 octane with your PSI so high? I thought anything over 140 PSI should at least be running 50-50.

 

Also...I hear the more ponies ... the harder shee is to shift. Might not be something to consider. Depending on your riding of course.

Been running pump gas with this setup for a year, no detonation, plugs, pistons,everything looks fine.

[duneloon]

I think with 150 you are pushing it. I would strongly recomend that you run 50/50. You should notice some gain, but I always run 110 with 180 lbs.

[1952]

Let me rephrase my question. Would bumping my compression from 150 to 180 yield an appreciable power gain to warrent additional cost, Race Gas , Less reliability , etc?

[dajogejr]

150 is borderline needing a mix of pump/race gas. if it's jetted properly, and you've been running it this way for a year...I'd say you're ok.

 

Bumping to 180 would obviously need race gas, as said...for more money. However...is it worth it?

You'd probably feel a little in the seat of the pants.

 

List all your mods...

 

And, have you had your crank trued and welded?

 

Also...I'm assuming you have an aftermarket head with changable domes...for the cost of a set of domes, 60 or 70 beans...you could always switch back and sell the domes for minimal investment if you didn't feel it was worth it...right?

[1952]

150 is borderline needing a mix of pump/race gas. if it's jetted properly, and you've been running it this way for a year...I'd say you're ok.

 

Bumping to 180 would obviously need race gas, as said...for more money. However...is it worth it?

You'd probably feel a little in the seat of the pants.

 

List all your mods...

 

And, have you had your crank trued and welded?

 

Also...I'm assuming you have an aftermarket head with changable domes...for the cost of a set of domes, 60 or 70 beans...you could always switch back and sell the domes for minimal investment if you didn't feel it was worth it...right?

My mods are listed in my original post , yes on the crank and thanks for the input

[dajogejr]

D'oh...and so they are...sorry bout that.

 

180 to 195 or so will be fine....as said, race gas for sure!

[1952]

D'oh...and so they are...sorry bout that.

 

180 to 195 or so will be fine....as said, race gas for sure!

Thanks for the help

[charles]

i run 180 psi in two of my bike for over a year now and no problem at all. with 91 octane!!!! I took my engine apart and every thing look in good shape.

[dajogejr]

i run 180 psi in two of my bike for over a year now and no problem at all. with 91 octane!!!! I took my engine apart and every thing look in good shape.

 

A...this thread is 4 months old, I'm pretty sure he's made his choice by now...

B...no two bikes are alike, but I think your compression tester is broke...

 

I've read/seen/heard of bikes in the 160's running premium pump gas, but 180...sorry, something isn't right in my book.

[sheefreak]

Must be running it rich as hell to mask that deto problem and losing valuable ponies in the process.

[Animalman294]

I agree with dajogejr on that, if you are runnin that kind of compression with 91 octane something is very wrong with that. If you are then you are running on borrowed time...............