My first race bike build!!!
- Thread starter deonsrace
- Start date
Look for air leaks, especially if the idle screw seems to have no effect.
Also check for a binding cable holding the slide open, or possibly the slide installed wrong.
The idle speed screw needs to be turned out to lower the idle, if you have the screw where it's ready to fall out or off the retainer spring, then it's time to look at the throttle cable and check that there's some slack in the cable at idle, it could be hung up because of a throttle cable that's too short or set too tight.
Check that it moves smoothly and free as well, any binding will be dangerous on the road.
Also check for vacuum leaks, this will make the idle go up as well and it leans out your mixture causing even more trouble. look inside the carb inlet and check that the slide is all the way down and closed, sometimes they can bind from needle misalignment and stick open, this only happens from poor and / or rushed assembly tho...
Check that it moves smoothly and free as well, any binding will be dangerous on the road.
Also check for vacuum leaks, this will make the idle go up as well and it leans out your mixture causing even more trouble. look inside the carb inlet and check that the slide is all the way down and closed, sometimes they can bind from needle misalignment and stick open, this only happens from poor and / or rushed assembly tho...
Find a spring to slide inside it like the bottom radiator hose on a car. This keeps it from collapsing.
The spring inside the hose should fix it, but if it doesn't you might need to get an elbow for that connection...
Ok so now i have everything set up on my bike and my carb keeps boging out on my its my tank. When i pull the throttle motor bogs out evey time. My tank drips gas to my mikuni but not enough gas to keep thebike going. What should i do now?
Fuel pump maybe?
Fuel pump maybe?
Did you let the engine warm up all the way before trying to ride it? Does it bog when you're on the bike or does it also bog with no load on the engine?
Will the engine rev better with the choke (enrichment knob) pulled on than with the choke off? the chokes on these carbs doesn't restrict airflow, but has a 3rd circuit that feeds the extra fuel needed for cold starts (some engines need to be warmed up pretty good before they'll rev).
Try this... Start the engine and let it warm up pretty good and see if it can rev... try it with the choke off, then try it with the choke on and see if it gets better. If it gets better with the choke on then you're definitely too lean and you can adjust the idle mix screw out a little more and see if it clears up, don't trust the factory recommendations here... there's a few ways to get your idle mix where it's supposed to be.
1. with engine warmed up and idling, turn the idle mix screw in until you hear it start to stumble, then turn it out the other way counting the turns until it stumbles on the rich side, now turn it in half the number of turns and you're set.
2. Same thing, engine warmed up and at idle, hook up a vacuum gauge and set it to max vacuum and you're set.
3. use a wideband o2 sensor and gauge, set your idle ratio to 12:1 - 14.7:1, listen for the best idle quality in between those numbers.
Method 3 is most accurate, and method 1 is least accurate, but still works... I recommend method 2 unless you can shell out $200 for a wideband setup as vacuum goes up as the air fuel ratio gets better. A vacuum gauge setup is pretty cheap and a really good tuning tool, a wideband is better but costs about 10 times more.
Your idle circuit stays in play on these type carbs for idle and low rpm cruising, then the main circuit gradually takes over while the idle circuit stays running so adjust your idle mixture first, then test it out and see if the problem went away.
If you still have bogging issues it's time to set the needle to the next higher position by removing it from the throttle slide and putting the E-clip one notch lower, reassemble and try again, between the proper idle mixture and the needle raised it should accelerate, but you may need to use the bottom notch on your needle.
The main jet only takes over at full throttle and if it's too small the engine will also bog or pop, spit, and maybe even backfire when reving the engine, you'll need to get a few different jets and go up a size and try it, then repeat until it's running right, accelerating clean with no bogging. If you go too rich you'll know by either a puff of black smoke when you gun it or a stumble then it clears up and accelerates.
Basically too rich and you'll feel it hesitate or stumble then accelerate, too lean and it'll bog or accelerate sluggishly. You can also get some cheap spark plugs and do some throttle chops to check what your mixture is doing by warming up the engine, get up to cruise speed and kill the engine rolling to a stop, pull the plug and put in a new plug (this is why I said cheap) the plug should be a light tan color, too dark= too rich, and too light= too lean. Repeat this at full throttle doing the same.
See if that helps, if not, let me know...
Will the engine rev better with the choke (enrichment knob) pulled on than with the choke off? the chokes on these carbs doesn't restrict airflow, but has a 3rd circuit that feeds the extra fuel needed for cold starts (some engines need to be warmed up pretty good before they'll rev).
Try this... Start the engine and let it warm up pretty good and see if it can rev... try it with the choke off, then try it with the choke on and see if it gets better. If it gets better with the choke on then you're definitely too lean and you can adjust the idle mix screw out a little more and see if it clears up, don't trust the factory recommendations here... there's a few ways to get your idle mix where it's supposed to be.
1. with engine warmed up and idling, turn the idle mix screw in until you hear it start to stumble, then turn it out the other way counting the turns until it stumbles on the rich side, now turn it in half the number of turns and you're set.
2. Same thing, engine warmed up and at idle, hook up a vacuum gauge and set it to max vacuum and you're set.
3. use a wideband o2 sensor and gauge, set your idle ratio to 12:1 - 14.7:1, listen for the best idle quality in between those numbers.
Method 3 is most accurate, and method 1 is least accurate, but still works... I recommend method 2 unless you can shell out $200 for a wideband setup as vacuum goes up as the air fuel ratio gets better. A vacuum gauge setup is pretty cheap and a really good tuning tool, a wideband is better but costs about 10 times more.
Your idle circuit stays in play on these type carbs for idle and low rpm cruising, then the main circuit gradually takes over while the idle circuit stays running so adjust your idle mixture first, then test it out and see if the problem went away.
If you still have bogging issues it's time to set the needle to the next higher position by removing it from the throttle slide and putting the E-clip one notch lower, reassemble and try again, between the proper idle mixture and the needle raised it should accelerate, but you may need to use the bottom notch on your needle.
The main jet only takes over at full throttle and if it's too small the engine will also bog or pop, spit, and maybe even backfire when reving the engine, you'll need to get a few different jets and go up a size and try it, then repeat until it's running right, accelerating clean with no bogging. If you go too rich you'll know by either a puff of black smoke when you gun it or a stumble then it clears up and accelerates.
Basically too rich and you'll feel it hesitate or stumble then accelerate, too lean and it'll bog or accelerate sluggishly. You can also get some cheap spark plugs and do some throttle chops to check what your mixture is doing by warming up the engine, get up to cruise speed and kill the engine rolling to a stop, pull the plug and put in a new plug (this is why I said cheap) the plug should be a light tan color, too dark= too rich, and too light= too lean. Repeat this at full throttle doing the same.
See if that helps, if not, let me know...
I like method 1.
And cheers Dave, that was very well explained,
I find the trick to method no 1 is to do as Dave says and get it idleing nice when its warm, but to fine tune it, leave it till the next morning, when the air is cool, and fine tune it then. that way as the temp goes up your idle is only a little rich, which will help to keep it cooler!
And cheers Dave, that was very well explained,
I find the trick to method no 1 is to do as Dave says and get it idleing nice when its warm, but to fine tune it, leave it till the next morning, when the air is cool, and fine tune it then. that way as the temp goes up your idle is only a little rich, which will help to keep it cooler!
Is the tanks cap breathing properly?
Can you drill the petcock?
Likely you could use a fuel pump from a mower engine, one of those square vacuum/diaphragm pumps?
Can you drill the petcock?
Likely you could use a fuel pump from a mower engine, one of those square vacuum/diaphragm pumps?
It doesn't take much fuel to feed a 212cc engine, as long as it's coming from the tank steadily it'll work, Have you removed the fuel petcock to check and see if the screen filter is clogged up? this happens on new tanks when the manufacturer doesn't clean out the tanks before shipping them out, Also any tank that's painted runs the risk of pieces of paint accumulating at the filter screen, sometimes enough to block flow.
Is the petcock valve of decent quality?
I've seen some where they shed off rubber from the valve everytime the fuel is shut off or turned on, these little rubber particles can block off flow inside the petcock, or migrate down into the carb and block off the needle and seat valve or jets when a fuel filter isn't used or if the valve is placed after the fuel filter. This happened to me with that "speed" carb where the valve is on the carb, it would run fine but cut out randomly until I found and fixed the problem.
If you're still having problems after your petcock is flowing ok, remove the float bowl on the carb and check for debris or paint flakes also, and check that the needle and seat valve isn't obstructed with anything, sometimes new carbs have debris in them like paing flakes, teflon tape pieces etc.
From what you're saying, try a different petcock valve and/ or check your gas cap vent, the fuel should come out in a steady stream, if it's just dribbling out it won't keep up with your carb, but if it's coming out of the petcock steadily and you're still having problems, then look into the other places I mentioned.
Is the petcock valve of decent quality?
I've seen some where they shed off rubber from the valve everytime the fuel is shut off or turned on, these little rubber particles can block off flow inside the petcock, or migrate down into the carb and block off the needle and seat valve or jets when a fuel filter isn't used or if the valve is placed after the fuel filter. This happened to me with that "speed" carb where the valve is on the carb, it would run fine but cut out randomly until I found and fixed the problem.
If you're still having problems after your petcock is flowing ok, remove the float bowl on the carb and check for debris or paint flakes also, and check that the needle and seat valve isn't obstructed with anything, sometimes new carbs have debris in them like paing flakes, teflon tape pieces etc.
From what you're saying, try a different petcock valve and/ or check your gas cap vent, the fuel should come out in a steady stream, if it's just dribbling out it won't keep up with your carb, but if it's coming out of the petcock steadily and you're still having problems, then look into the other places I mentioned.
Got the carb tuned and figured out. When the carb was shipped the fuel line was on the breather and i assumed thats where it belonged. Carb works pefect now. I trimmed the fuel line and no more issues with the bike not starting.
Now i need to figure out for the jackshaft any ideas?
Now i need to figure out for the jackshaft any ideas?
Excellent, with a brand new engine there's always some little issue to get past before they run, glad it was something simple...
What's there to figure out with the jack shaft? I thought you already had that part the way you wanted it?? I'm sure I got a few more tricks up my sleeve... let me know...
What's there to figure out with the jack shaft? I thought you already had that part the way you wanted it?? I'm sure I got a few more tricks up my sleeve... let me know...
Maybe get rid of the radiator clamps and replace with T bolt clamps, they're considerably stronger, won't strip out, and look a lot better
I find it much easier using pillow blocks bolted to an aluminum plate that's bolted to the seat tube with an exhaust type clamp or similar. Then if things don't stay put I'll add spacers and/or locking clamps as needed. I also drill and tap the ends of the jack shaft and install a bolt and washer to keep anything from coming off the end of the shaft. It's just a good idea as things can come loose and you just don't want parts flying off the drivetrain.