Ok,
Just went from a stock head, piston and cams to a mildly ported head, HPR HR2 cams, and an 11.5 JE piston.

I was already running a TM45 carb, Big Gun CDI, no Airbox with a NoToil filter and ported intake.

I was jetted right on, at 2500', with a 160 Mikuni main jet, and was wondering if anyone could recommend a main jet to start with for breaking tomorrow.

Scott

 

your shooting in the dark on tuning unless you get you an egt meter to monitor, it is cheap compared to a messed up motor , some built motors will like a leaner jet than stock believe it or not, all you can do is read plugs if no meter, and depending on your fuel choice that will be difficult also these days, one spends a lot of money on these builds, an added necessary product for a couple hundred bucks is an EGT meter to tune these builds, you spent the money elsewhere on the build, a meter is the first thing to buy,
MY 2 cents.

 

I understand where you are coming from XR.

Do you prefer the EGT over an O2 fuel/air ratio meeter? It would be nice to have something so that when I go from 2500' to 6000' or sea level I could do a quick check and be right on.

But, I have neither at this point, and thats why I'm asking for someone with more TM45 time to throw in their 2 cents.

The 160 main I was using was based on an O2 meter while dyno tuning, with plug check follow up.

 

Since nothing changed on the exhaust, intake and ignition; these are the major players in jetting; I would think that jetting up one size to balance the increase flow at top end would be fine.

OMR

 

My ported head I jetted leaner, Better signal pulled more fuel no all heads are the same some will require richer. With ported head theres no way to tell without a meter of some sort. Start way rich and lean down. Beter safe than sorry.

 

Well, I went up to a 165 to play it safe, did not seem rich, not rich enough to wash the rings which was my worry. That and being to lean and pinging with the 11.5 piston.

I have around 30 minutes on it now, mostly between 2,500 and 5,000 RPM. And 1/4 to 3/4 throttle.

Going to do the same for the next 1/2 hour and then change the oil and let it rip.

Thanks all,
Scott