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CP17.5mm swap anyone?

Posted: Sat Jul 12, 2025 7:43 pm
by robokirby
Just finished putting back together my spree.

Starting to sort out the tunning, curious is anyone else has used a Polini CP17.5mm on a Spree and has found any good jetting, just looking for some loose recommendations.

So far on the set up I have it built as;
Stock cylinder
carbon reeds
Polini CP17.5mm carb /w Polini CP compact filter
MLM exhaust
SSS Spree Speed Pulley

I have the 38 pilot
Needle is 1 up from center (leaner)
Air screw is 1.5 turns out.
And right now I have a 88 jet in there.

Starting bigger on the main just cause I can't seem to find any examples of anyone else running this carb I know it's only slightly bigger but I think with the air filter being a lot more flowing it's gotta need someone more than when people use the stock carb/airbox and are running 72 or 74 main jets.

With the 88 main it feels sputtery on WOT, I have a 85 so I am going to try that. Just waiting on a new rectifier right now as I realized mine is bad and my battery is not charging.

I do have a CHT on there too so I can try to keep an eye on the temps.

Curious if anyone else is running a similar set up and what their experience has been?

https://imgur.com/gallery/honda-spree-cp17-5mm-j2J2DG5

Re: CP17.5mm swap anyone?

Posted: Tue Jul 29, 2025 9:03 pm
by robokirby
Okay so had to take a break from tuning as I realized my oil pump seal was shot and it was slowly leaking oil into the crankcase making it harder to start and a smoke show when it did start up.

Ordered a seal replacement kit and replaced all the seals, and now we're back in business.

Today I lowered the pilot jet to a 36, which I should have figured as that is what I have in my dio, and my dio has a BBK.

Anyways with the 36 pilot, needle moved one clip up from middle, and 85 main the idle to mid throttle is a lot cleaner sounding. 3/4 to WOT is still quite bubbly overall so I think the 85 pilot jet is still too big. I have an 82 and 84 so I'll try those over the next few days.