Mikes keihin carb kit

[pamcopete]

bobber33,

Well, I'm not the expert on exhaust, but I think that you need some back pressure for optimum performance. Perhaps the grizld1 will come back here with his expertise on the subject.

The altitude in La is only 377 feet, so if anything, that produces even more flow.

 

[bobber33]

bobber33,

Well, I'm not the expert on exhaust, but I think that you need some back pressure for optimum performance. Perhaps the grizld1 will come back here with his expertise on the subject.

The altitude in La is only 377 feet, so if anything, that produces even more flow.

I live around 750 feet, and i can ride in half an hour to 2000 feet,,, its crazy.

The bike feels good from idle to 1/4 throttle. But if you open it up it doesn't seem to pull properly. Kind of sputters and acts like its trying but just cant get to it. The smaller main jet is an improvement but still not right. These are very short rides i'm taking to test it, and it is definitely making the plugs black in a very short amount of time.
So i'll order mains, a couple different steps down and see what happens i guess...
Pilot and needle seem about right it's mainly when you open it up.

 

[grizld1]

"Back pressure" is one of those terms that sounds good but doesn't mean a lot, Pete; it confuses a number of exhaust issues. The only back pressure that's a good thing is the resonant pulse of a tuned exhaust, alternating a "push" to hold the fuel charge with a "pull" to scavenge spent gasses,and that's strictly a function of primary length. In terms of jetting, freeing up exhaust and/or intake flow will lean the mix, and that clearly isn't the issue here. If there are baffles crammed in those straight pipes, they could be creating enough restriction to foul things up. Bobber33, be sure to check float level if you haven't done it already.

 

[toepfer]

I don't mean to hijack this thread with my own question, but does anybody have any ideas here?

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.

 

[toepfer]

bobber33 you and I have a seemingly opposite problem ... mine has tons of power with lots of throttle, and seems to hesitate before 1/4 throttle.

 

[bobber33]

bobber33 you and I have a seemingly opposite problem ... mine has tons of power with lots of throttle, and seems to hesitate before 1/4 throttle.

Needle adjustments are simple so try moving the clip up one notch and see if its better or worse if worse then go the other way.

 

[bobber33]

also if its not returning to idle properly you may have a vacuum leak, check your gaskets and your vacuum plugs to make sure they aren't sucking air. I've noticed on mine after removing the vacuum caps the barbs have pulled completely out and needed to be re-glued in.

 

[Jack]

Toepfer.. Go up on the pilot jet and lower the clip on the jet needle. Any time you have a hesitation on take off,it's one of the two I've mentioned most likely the jet needle will solve it. The dieing at a stop light is either timing or pilot jet circuit to lean.

 

[Jack]

Bobber.........great looking rides man your problem with the jetting will most likely be those rigged baffles. Never could understand why some cram baffles up straight pipes,does more harm than good.

 

[5twins]

If your idle speed is set too low, these bikes will just up and die at stop lights for no apparent reason. Best to stick to the 1200 RPM factory spec.

 

[bobber33]

Bobber.........great looking rides man your problem with the jetting will most likely be those rigged baffles. Never could understand why some cram baffles up straight pipes,does more harm than good.

My baffles are only 2" long. I cut them down so they are barely doing anything. Just enough to quiet it down a bit. Reason for them is obvious... its too loud without them and i don't need the LAPD beatin me down everytime i ride it.

 

[grizld1]

Aha--thought so! Bobber33, your white bike has cocktail shaker muffs and has power, and your black bike has baffles crammed in the straight pipes, runs too fat, and has no power. Do I need to say more? The motor's telling you those baffles are doing plenty, and it ain't happy about it! To operate with that much restriction you'll need to lean out your jetting, and you'll still be down on power on the hotter motor. A 2" long baffle in a 4" diameter muffler might not do much, but crammed into a straight pipe it's another matter entirely.

 

[bobber33]

Aha--thought so! Bobber33, your white bike has cocktail shaker muffs and has power, and your black bike has baffles crammed in the straight pipes, runs too fat, and has no power. Do I need to say more? The motor's telling you those baffles are doing plenty, and it ain't happy about it! To operate with that much restriction you'll need to lean out your jetting, and you'll still be down on power on the hotter motor. A 2" long baffle in a 4" diameter muffler might not do much, but crammed into a straight pipe it's another matter entirely.

I understand what your saying although the baffles were not in the pipes for the first few rides when i finished building it. They were put in after just for noise reasons (neighbors). I'll pop em out and let u know. But far as i can remember it felt the same with our without them. Just allot louder.

 

[toepfer]

Toepfer.. Go up on the pilot jet and lower the clip on the jet needle. Any time you have a hesitation on take off,it's one of the two I've mentioned most likely the jet needle will solve it. The dieing at a stop light is either timing or pilot jet circuit to lean.

so that will bring the needle up, and allow more fuel to accumulate there, enriching the pilot circuit? i still consider myself a noob, so all of this help is great.

i will check my gaskets as well for vac leaks. if i twist the throttle a couple of times...the first time, it returns, the 2nd time it returns, the 3rd it might hesitate on return. noticed that after riding and pulling into the garage.

thanks all.

 

[Jack]

so that will bring the needle up, and allow more fuel to accumulate there, enriching the pilot circuit? i still consider myself a noob, so all of this help is great.

i will check my gaskets as well for vac leaks. if i twist the throttle a couple of times...the first time, it returns, the 2nd time it returns, the 3rd it might hesitate on return. noticed that after riding and pulling into the garage.

thanks all.

The pilots functions up to quarter throttle and (the jet needle chimes in from one eight to three quarters throttle and this is most likely the area where the A/FR is running lean) by lower the jet needle clip you raise the needle allowing more fuel to enter the needle jet thus hopefully fattening up the mixture to eliminate that hesitation feeling you're experiencing. Also make sure your RPMs for idle are correct as 5Twins has suggested.

If your Xs has the original ATU,it maybe sticking or centrifugal weight return springs have lost some of their tension,which is common,just clip one coil off,if that is indeed your throttle sticking problem.

 

[Goldy]

I've been chasing my tail for the past three years trying to get the carbs sorted out on my old 650...the left carb works perfectly, but the right side just won't play. Anyhow, I was thinking of fitting a pair of Amals to it when I came across the replacement carbs Mike's sells. One of these kits arrived today (Jan 10th), looks like a well thought out set up...however, I don't think I will tease myself by installing it just yet...it's too damn cold and snowy to ride, might as well wait 'till spring is a little nearer...I wish I lived in Arizona.
When the weather warms up enough to install them and test ride, I'll report back.

 

[bobber33]

Aha--thought so! Bobber33, your white bike has cocktail shaker muffs and has power, and your black bike has baffles crammed in the straight pipes, runs too fat, and has no power. Do I need to say more? The motor's telling you those baffles are doing plenty, and it ain't happy about it! To operate with that much restriction you'll need to lean out your jetting, and you'll still be down on power on the hotter motor. A 2" long baffle in a 4" diameter muffler might not do much, but crammed into a straight pipe it's another matter entirely.

Thanks for all the help.
Ok got home early and took out the baffles, went for a rip around the block.
There is definitely a difference. There is more power but still not 100% i'm probably only off by 1 jet size at this point no big deal i'll figure that out.

Although now with straight pipes its way too loud for my friendly LA cops... so what am i suppose to do now? If i rig up mufflers or something i'm gonna be back in jetting hell right?

 

[grizld1]

"Jetting hell?" Not really. A pair of free-flowing muffs with smooth core glasspack baffles will be far less restrictive than the inserts you're using. You'd have to cut the turnouts off those pipes, though, maybe find muffs that give a bit of an upkick or use an angled adapter to keep 'em off the ground. Jetting just takes time, patience, and a firm understanding of the fact that every change you make affects everything else, so that you think of tuning in tightening circles rather than a straight line. Avoid the tiny muffs with mechanical baffles: they're both restrictive and noisy, with a raspy, unpleasant tone.

 

[Lunatic]

Thanks for all the help.
Ok got home early and took out the baffles, went for a rip around the block.
There is definitely a difference. There is more power but still not 100% i'm probably only off by 1 jet size at this point no big deal i'll figure that out.

Although now with straight pipes its way too loud for my friendly LA cops... so what am i suppose to do now? If i rig up mufflers or something i'm gonna be back in jetting hell right?

Have you got the little baffles like these?

If so, you might want to try pushing a 1/4 inch steel rod down the middle of them to open them up a bit. A local builder here uses them and opens them up just a bit and has found they sound better and work better.

 

[toepfer]

...

so, i lowered the clip (raised the needle) 1 position, now the bike seems to idle fine at rest once I start it, but as soon as you get it going, it doesn't like slowing down ha!

but seriously, i got off the throttle and the bike will run/roll/cruise in all gears with no throttle??? i can only think that it is getting too much fuel to the pilot circuit now, as if it is running with choke on?

the mixture screw is 1 turn out

i plan on spending some significant time with this... but I can still use some help