Installing bigger jets

"From what I am reading it seems that this can be omitted? Is this true?"

From what I understand from WG, that is correct. I believe it was an EPA emissions thing. Eliminating that that would bring your carbs back to "standard" 650 specs. For example, my bike came with 90 something jets stock, I now run the "standard" 102.5's (stock air box and exhaust) and it runs great. Getting near 1980 they tried to lean things out, such as horsepower and drivability!

anarki650 wrote:

With pod filters and 4-1 with stock carbs on my 77 b1 I was running 17.5 pilots (15 is stock size) with the needle clipped at the #4 slot and 115 mains. With no baffle in the pipe I had to up the main to 117.5. This set up gave me perfect plug chops on all three circuits. As was stated, jetting is a PITA and to get it right you almost have to do a plug chop on all three circuits to make sure that you're not lean somewhere and rich somewhere else. The idle circuit is the easy one to get right, because if it idles and doesn't hesitate when you crack the throttle you're pretty much right on. The needle and main jets overlap eachother and it can be a bit of trial and error to get those right. You might very easily be lean on the needle (mid range) and too fat on the main and never really know unless you spend some time tuning. With the previously mentioned jets my bike didn't hesitate at all, she jumped to life when you twisted the throttle from idle and screamed like a raped ape all the way to redline.

When I changed from the stock vm24 carbs to vm26's my jetting didn't change at all. I assumed it would and tried many different configurations before realizing that the same jetting was what my bike wanted even with the bigger carbs.

Make sure you sync them good too! You'll have a hell of a time getting rid of sputters and hesitations if the carbs aren't synced properly.

When you say slot #4, is that the 4th slot from the top, or the bottom?

4th slot down will richen up the midrange 4th slot up will lean it out.

Ah. Thanks

In the context of what anarki650 said, did he mean 4th from the top or bottom?

Hows the re-jetting going? Any results yet? I'm doing the same thing for my VM 24 Mikuni's now on my '78 kz650. I bought the bike a few months ago with pods on it already. I just opened up the carbs today and found my main jet is at 102.5 and my pilot is at 17.5. I'm basically at or around sea-level for the most part. Give or take a 100 metres. I'm running a 4 to 1 exhaust as well. If anyone has any jetting insight into this configuration I'm all ears. I have a set of 110 and 115 mains kicking around that I'm thinking of trying out.

Sorry I didn't see this sooner... I was referring to #4 from the top (second to the bottom) slot.

Hope you got her all sorted out!!!

alexnelson wrote:

Hows the re-jetting going? Any results yet? I'm doing the same thing for my VM 24 Mikuni's now on my '78 kz650. I bought the bike a few months ago with pods on it already. I just opened up the carbs today and found my main jet is at 102.5 and my pilot is at 17.5. I'm basically at or around sea-level for the most part. Give or take a 100 metres. I'm running a 4 to 1 exhaust as well. If anyone has any jetting insight into this configuration I'm all ears. I have a set of 110 and 115 mains kicking around that I'm thinking of trying out.

Is the 4-1 baffled or not? If it's baffled I'd drop in the 110s and see how she runs up towards redline. No baffle go with the 115s.

I am waiting on my carb rebuild kits from oldbikebarn.com

I ordered a few jet sizes off of z1 enterprises though. I'll have a set of 110s, 115s, and 117.5s, I believe (debating if I should have gotten the 112s too). I also bought a set of 17.5 pilots.

My exhaust isn't 4 into 1 though. I have an exhaust system with two mufflers. I have headers that take the exhaust from cylinder 1 and 4 out the left side, and then 2 and 3 out the right side. I believe the headers were made by Jardeen back in the day.

Any recommendations based on my exhaust?

anarki650 wrote:

Is the 4-1 baffled or not? If it's baffled I'd drop in the 110s and see how she runs up towards redline. No baffle go with the 115s.

It's a baffled 4-1.

I put the 110's in and got the carbs back on the bike. Took me two nights of kick-starting to get the thing fired up again (for some reason my electric starter never seems to start the bike) and now she only runs between 1500 and 2000RPM. Anything lower or higher and the engine sputters and dies. I have to keep the choke at half way for the engine to stay on. Needless to say I can't even get out of the driveway.