Coming from Mike's I was wondering if they were going to hold up. Are they the same size as stock carb holders? If so the JBM Industries holders should work.
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Mikes keihin carb kit
- Thread starter bigpup
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- carburetors
How about www.jbmindustries.com
freebird
Ritchie
I have been restoring a XS Special 1980G model, it has a fairly freeflow exhaust and i have fitted Mikes Keihin carbs to it with no real problem. However now i seem to have a jetting problem. It was missing at mid range revs, so i changed the 35 main jet to 30 and that made it worse and it had black plugs after a run. I put a hotter set of plugs into it
BP 6ES instead of the BP 7es that were in the bike. It was a big improvement but it still has a miss a mid revs and high revs. I am now wondering about putting the 40 main jets in to see what that does. An ideas. Freebird
BP 6ES instead of the BP 7es that were in the bike. It was a big improvement but it still has a miss a mid revs and high revs. I am now wondering about putting the 40 main jets in to see what that does. An ideas. Freebird
pamcopete
Ride.Enjoy.Life is Simple
freebird,
What kind of exhaust system / muffler(s) do yo have?
What kind of exhaust system / muffler(s) do yo have?
1. You don't cure fuel-blackened plugs by jetting larger.
2. You're stepping up your pilot jets, not your mains.
3. With a couple of exceptions (main circuit transition in vacuum diaphragm carbs, main
air jet selection in carbs so equipped, which your aren't) you pay attention to throttle
position when you're jetting, not rpm's.
2. You're stepping up your pilot jets, not your mains.
3. With a couple of exceptions (main circuit transition in vacuum diaphragm carbs, main
air jet selection in carbs so equipped, which your aren't) you pay attention to throttle
position when you're jetting, not rpm's.
I've been running into a problem as well...
the bike:
1979 special
2 into 1 tracker style pipes with a rev. cone megaphone that mikes recommended with the header setup.
it was running pretty lean at first (wouldn't return to idle and already colored the pipes a bit on the first couple miles! so, swapped both jets to one step larger. did NOT adjust the needle position. adjusted the cable routing and adjusters, lined up the slides top and bottom.
mixture screw out 1.5 turns.
it starts first kick, but likes a little throttle when you do it.
it seems to idle fine, maybe a little low. I've adjusted and balanced it while sitting, it's only when i'm stopped at a light that it seems a bit low.
a little hesitation at take off, occasionally wants to die at a stoplight
but, i definitely still feel a lag in returning to idle in gears 2,3,4.
it runs fast, loud, and pretty damn dependable thus far...but can't tell where to go from here. i could run spark tests all day trying to get it right, but if anybody has a suggestion, i'm all for it. i want to go for a longer ride, but it's only about 15-20 minutes into the ride that it starts to idle funny.
the bike:
1979 special
2 into 1 tracker style pipes with a rev. cone megaphone that mikes recommended with the header setup.
it was running pretty lean at first (wouldn't return to idle and already colored the pipes a bit on the first couple miles! so, swapped both jets to one step larger. did NOT adjust the needle position. adjusted the cable routing and adjusters, lined up the slides top and bottom.
mixture screw out 1.5 turns.
it starts first kick, but likes a little throttle when you do it.
it seems to idle fine, maybe a little low. I've adjusted and balanced it while sitting, it's only when i'm stopped at a light that it seems a bit low.
a little hesitation at take off, occasionally wants to die at a stoplight
but, i definitely still feel a lag in returning to idle in gears 2,3,4.
it runs fast, loud, and pretty damn dependable thus far...but can't tell where to go from here. i could run spark tests all day trying to get it right, but if anybody has a suggestion, i'm all for it. i want to go for a longer ride, but it's only about 15-20 minutes into the ride that it starts to idle funny.
freebird
Ritchie
The mufflers are MCS
freebird
Ritchie
Thanks for the help mate, "yes you are right" i changed the pilot jet instead of the main. Oh well do it again.
OK i have a question...
Some of you know my bikes when i say white one or black one so here is my question.
My white bike uses 34mm mikuni's and the black bike is using these mikes keihin carbs.
I thought i had the black bike running great - UNTILL i took the white bike out for a rip the other day.
White bike KILLS the black one in power? the only difference is essentially the carbs? Literally will pull you off the seat if you don't hold on tight.
Black bike runs good, but doesn't seem to have anywhere near as much power?
I've re-jetted the keihins both up and down - both pilot and main's, and there is some difference but nothing night or day?
SO i guess i'm asking is there that much of a difference between an 1980 XS650 and a 1972? both bikes are almost identical engine wise, and both have similar compression. So are these carbs not working right or do the mikuni's just work a hell of a lot better?
Or am i missing something else?
Some of you know my bikes when i say white one or black one so here is my question.
My white bike uses 34mm mikuni's and the black bike is using these mikes keihin carbs.
I thought i had the black bike running great - UNTILL i took the white bike out for a rip the other day.
White bike KILLS the black one in power? the only difference is essentially the carbs? Literally will pull you off the seat if you don't hold on tight.
Black bike runs good, but doesn't seem to have anywhere near as much power?
I've re-jetted the keihins both up and down - both pilot and main's, and there is some difference but nothing night or day?
SO i guess i'm asking is there that much of a difference between an 1980 XS650 and a 1972? both bikes are almost identical engine wise, and both have similar compression. So are these carbs not working right or do the mikuni's just work a hell of a lot better?
Or am i missing something else?
pamcopete
Ride.Enjoy.Life is Simple
bobber33,
Well, it might be a lot of trouble, but the only way to find out if its the bikes or the carbs is to swap the carbs from bike to bike.
Well, it might be a lot of trouble, but the only way to find out if its the bikes or the carbs is to swap the carbs from bike to bike.
ya its a pain.. didn't want to remove cables and throttles re/sync etc... but has anyone else compared these to a mikuni for performance?
What year bike has what carb and type of camshaft? Depending how the ports where formed from factory casting has a huge influence how the the ports flow and regardless whether its a roundslide or flatslide you have 2mm difference in venturis volumes,the 34s will out flow the 32s.
gonna mess with it a bit more tomorrow (timing/jetting etc...) . But no way it's gonna cause what feels like a 20hp difference...
Actually the 1972 keihin bike has bigger pistons and better valves. Cams are stock for both so nothing really left but the carbs. Both engines rebuilt the same also.
If i ever get around to swapping the carbs this may be the ultimate test for these things.
Maybe worth finding mikunis as far as i can tell. Plus the idle is much nicer on the mikuni bike.
pamcopete
Ride.Enjoy.Life is Simple
I've installed these on my '81/H, replacing the stock BS34's and I "felt" that the Keihin's produced more power that was very noticeable.
Mike also mentions that the carbs will really perform better with a freer flowing exhaust.
You should also check that your timing is advancing properly and that the advance rod is not binding. Here is a video showing the snap back that you should have.
bobber33, there are performance differences between the 72 and the 80--the 72 has a hotter cam and lighter frame, and other things being equal should be the faster of the two. But as Pete "points" out, the contact breaker ignition on the 72 introduces a few possibilities for error that aren't present with the TCI system in your later mill. As Jack notes, the 34 will flow more mix, but this would have an impact only at high rpm and really shouldn't be anything you'd feel in the seat of the pants. Another possibility--your 72 has been rebuilt (oversize pistons). If you (or whoever did the top end) used an Athena or XS Performance head gasket, the deck got raised .012" higher than the .048" OEM gasket. That change advances valve timing and murders performance.
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OK so messed with it a bit today heres the outcome...
Timing is damn close (checked with light). Advance is working properly.
Its gotta be running too rich with the jets provided.
I put the 130 main jet in and the 40 pilot with needle at stock center position.
Runs like a bag of shit when you get on the gas hard in 2nd gear it sputters and falls on its face.
Plugs are black with carbon.
With the 120 main and 30 pilot and needle dropped 1 notch
Its smoother and seems much better but still feels super FLAT when hard on the throttle still has a few sputters too. Plugs still black/ish.
These are all the jets i have for these carbs so i guess i'm gonna have to buy some smaller jets? any suggestions?
Timing is damn close (checked with light). Advance is working properly.
Its gotta be running too rich with the jets provided.
I put the 130 main jet in and the 40 pilot with needle at stock center position.
Runs like a bag of shit when you get on the gas hard in 2nd gear it sputters and falls on its face.
Plugs are black with carbon.
With the 120 main and 30 pilot and needle dropped 1 notch
Its smoother and seems much better but still feels super FLAT when hard on the throttle still has a few sputters too. Plugs still black/ish.
These are all the jets i have for these carbs so i guess i'm gonna have to buy some smaller jets? any suggestions?
pamcopete
Ride.Enjoy.Life is Simple
bobber33,
What exhaust are you running?
What exhaust are you running?
on this one its straight duals no mufflers, just a couple small baffles.
I'm in LA so maybe its an altitude thing also.
