Suggestions on jetting

[bikerphil]

It's probably your pilot circuit, below 4K rpm that is running rich. The 130 is way too small main for the early type carbs. The mains kick in over 4K rpm. Have you cleaned the carbs thoroughly? Verify the type of pilot you are running. If you have the wrong type, it'll run rich in the low range.

[dragxs11]

Depends on whether your rich on idle or rich on throttle.
Get the idle mixture right first. And, as it's been said, a 42.5 from this manufacturer probably isn't the same as a 42.5 from that one. Thats why I use the drill bit test.

[bikerphil]

This picture will help you determine if you have the correct type of pilot jets...

http://www.mikesxs.net/products-39.html#products

[dragxs11]

This may help me too, as I'm looking for pilot jets right now. Phil... your saying that the mikesxs 42.5 BS30/96 IS the proper size???

[clcorbin]

At lunch, I ran home and pulled apart one of the clean carbs and took a few pictures. Here is the inside of the bowl area showing the main jet and the screw covering the pilot jet:



The pilot jet is definitely a BS type. It is marked 42.5 on the base:



Does this clarify what I have? The main jet is a 130 and the pilot jet is a BS 42.5. I did NOT take out the air bleed and get it's number, but I can if it is needed.

[bikerphil]

Dragster, yes those are the proper type. 42.5 is the stock size. Some folks go up to a 45 depending on what exhaust and air intake they're running.

Corbin, those pilots look like the right type, but can cause problems if they aren't genuine Mikuni, same with the mains. The 130 you have could be a Dynojet which uses a different # system. If it was me rebuilding those, I'd get all new Mikuni jets fron Mikesxs for $25 and they will work for sure. Air jets should be 180, IIRC.

[dragxs11]

OK, thanks Phil.
Just wanted to make double sure. My dealer failed to restock after the last time I bought what they had. Just need the pilots and intake boots and the "stocker" will be running and ready to sell.

[clcorbin]

I just ordered the 130 jets from MikesXS along with the 42.5, 40, and 37.5 pilots (just in case). It is very possible my current ones are dynojet jets. I will see how this goes and then tweak things from there.

[dragxs11]

Ya Clint,
I'll stick my neck out and say that pilot jet hole looks bigger than it should be. Compare the two when you get the new ones. Years ago, I went through the same issue. Like and idiot, I tossed the original jets and, back then, called Bob Jones(Merriam Cycle) and got bonified OEM's(used).

[dragxs11]

Got my 42.5 pilots from Mikes today. Checked them against the factory ones I pulled out and the new ones were too small. Better that than too big.

[clcorbin]

My new jets came in a couple of days ago. The carbs have been put together and reassembled. From looking at the pilot jets, it DOES look like the new ones are a bit smaller than the old ones. I don't have any wire feeler gauges, so I didn't measure the openings. But visually, it does look a bit smaller on the new pilots.

I noticed something else this round: The outer mains where 127.5 and the inners where 130s. I put new 130s all the way around, so we shall see how thing work out with the mixture once I get the idle circuit fine tuned.

At this point, I am really looking forward to getting this thing put back together and on the road. She hasn't had this much TLC in the last 20 years. I can't wait to see how she runs.

[dragxs11]

Stock setup runs the inner cylinders a bit richer to keep them cooler. Shouldn't be a problem but this is one reason an oil cooler gives good peace of mind.