high compression headswap jetting?

[shane_lxi]

I was reading in the wiki about swapping the head off an 84-85 spree onto a later model for a bit higher compression. I have an 84 parts bike, so I'm thinking of giving this a shot. What size jet would be recomended for this swap? Thinking of maybe shaving around .010 off also.

[Trafficjamz]

Not really sure you need to upjet.

Do run premium fuel if compression goes past 140psi

[Bear45-70]

I agree with TJ. Jetting should not be an issue.

[shane_lxi]

Thanks for the help guys! It definately check compression once the head goes on. I'll update this thread if this ends up working out!

[Trafficjamz]

Thanks for the help guys! It definately check compression once the head goes on. I'll update this thread if this ends up working out!

Oh it works alright

I don't think you have to shave .010 off of the head though

[Bear45-70]

I was under the impression that you shaved the '86-'87 head .020" and just swapped on the '84-'85 head. no shaving required.

[shane_lxi]

Awesome, even better if I dont have to take a trip to the machine shop. Thanks alot guys! Ordered my headgasket today, so as soon as that get's here, I'll pop the '84 head on there and try it out . I love freebies!

[Trafficjamz]

Awesome, even better if I dont have to take a trip to the machine shop. Thanks alot guys! Ordered my headgasket today, so as soon as that get's here, I'll pop the '84 head on there and try it out . I love freebies!

My friends 1987 spree had a compression reading of 125psi.

Swapped to a 1985 head and the reading was 150psi

[shane_lxi]

Any problems with rings or anything after the swap? That's a pretty big jump in compression.

[Trafficjamz]

Any problems with rings or anything after the swap? That's a pretty big jump in compression.

Belt and clutch slippage from the newly added power was the only issue.

[shane_lxi]

That much more power gain eh? I put ax24 vbelts in our bikes today, and lost 2mph off the topend for some reason, so I put our stock belts back in. Sooo, if I slip, I'll try and get a new oem belt. I don't think my clutch will slip @1200miles, but who knows til I'm there .

ps: ax24's are supposed to be 1/2"x24" right? My Gates ax24's are 1/2"x26", not sure if maybe that's the cause of power loss or not?

[Trafficjamz]

That much more power gain eh? I put ax24 vbelts in our bikes today, and lost 2mph off the topend for some reason, so I put our stock belts back in. Sooo, if I slip, I'll try and get a new oem belt. I don't think my clutch will slip @1200miles, but who knows til I'm there .

ps: ax24's are supposed to be 1/2"x24" right? My Gates ax24's are 1/2"x26", not sure if maybe that's the cause of power loss or not?

Did you measure the inside or the outside?

[shane_lxi]

I didn't measure, package was labeled 26", prolly outside, but it is noticably bigger diameter than stock.

[Bear45-70]

The stock Spree belt is 24.7244" X 0.4488", so a 26" belt is only 1 1/4" bigger for the pulley mod.

[spewya]

i have a sb50p and if i do pully mod by putting a se50p clutch in it and cutting the case will i need a longer belt and how much do i mill down the front inner pully

The stock Spree belt is 24.7244" X 0.4488", so a 26" belt is only 1 1/4" bigger for the pulley mod.