I’ve purchased parts from JBM before. Good service and quality parts.
http://jbmindustries.com/index.html
http://jbmindustries.com/index.html
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‘77 BS38 running way too lean
- Thread starter cjv2001
- Start date
I've heard the JBM manifolds are strong enough to run without the metal shrouds. But, do save them in case you ever do find nice originals. The original manifolds need the added support of the metal shrouds, especially if you've removed the airboxes and are running pods.
Thanks, that seemed to work! The bike is not starting good now with the mix screws almost all the way in, and smells of gas. could be a good sign that it is way too rich now. Going to pop some 27.5 pilot jets in. And go from there
Yes, downsize the mains as well. 140's are way too big. And did you ever take pics to show us? And have you checked the needles and needle jets to make sure they are correct (4M1 needle and Z-8 needle jet)?
One more thing - the float level spec for the '76-'77 carb set is 25mm. If you're set at 24mm, that's a richer setting.
OK, you definitely have '76-'77 carbs there. Yes, it's tough to read the size of the needle jet unless you pull it out because it's stamped in the side of that lip .....
But yours look pretty dirty inside so pulling them out for a good cleaning may not be a bad idea. And all those little holes down the side are air bleed holes. If they're plugged, it will run rich.
Did you happen to get a pic of the tops of your float bowls, where the pilot jets install? I ask because there were two bowl types, one for the BS30/96 pilots and one for the VM22/210 pilots. They will swap but you need to use the correct one for your carb set and the pilot type it uses. The difference is in how the air is delivered to the pilot jet .....
On the BS30/96 bowls, the air is delivered to the bottom of the jet through an angled passageway, and the jet flows the resulting fuel/air mix. On the VM22/210 bowl, the jet flows straight fuel and the air is added afterwards, on top of the jet. This explains why the VM22/210's are sized so much smaller (in the mid to upper 20's) compared to the BS30/96's (sized in the low to mid 40's). Your '76-'77 carb set uses VM22/210 pilot jets and their matching bowls.
But yours look pretty dirty inside so pulling them out for a good cleaning may not be a bad idea. And all those little holes down the side are air bleed holes. If they're plugged, it will run rich.
Did you happen to get a pic of the tops of your float bowls, where the pilot jets install? I ask because there were two bowl types, one for the BS30/96 pilots and one for the VM22/210 pilots. They will swap but you need to use the correct one for your carb set and the pilot type it uses. The difference is in how the air is delivered to the pilot jet .....
On the BS30/96 bowls, the air is delivered to the bottom of the jet through an angled passageway, and the jet flows the resulting fuel/air mix. On the VM22/210 bowl, the jet flows straight fuel and the air is added afterwards, on top of the jet. This explains why the VM22/210's are sized so much smaller (in the mid to upper 20's) compared to the BS30/96's (sized in the low to mid 40's). Your '76-'77 carb set uses VM22/210 pilot jets and their matching bowls.
Thank you for this. I will clean the needle jet, I blew it out with compressed air but will try to clean the gunk out. For my float bowls. They are the VM22/210 bowls. The bike seems to be running very rich now after the JBM’s so I think from now it’s some fine tuning with different jet sizing. I leaned the needle into the 2nd slot. There doesn’t seem to be any more pops. I’ll try to upload a small video I took.
Order these from niche cycles
Yes, the BS38s use the very common and widely available N102.221 "small round" mains ......
Perfect thank you!
Yessir, just ordered them from Niche Cycles. Will post a vid once I get everything running good. Thanks for all the help everyone
Buy a range of jets. Two sizes up and down from stock
Put a 25, and a 127.5 in. Bike started fine, took it for a ride and shifted into 2nd. Immediately revved extremely high up to 6k rpm. Now whenever I start it it constantly revs that high and have to kill it right away
Sounds like the throttle cable is messed up, hanging up somewhere.
