TOPIC:

hardrockminer wrote: These documents may be helpful in understanding how a carb works and how to rebuild them. Note that in the disassembly document he calls the diffuser a needle jet. I believe the needle jet actually sits up in the main jet chamber, and is partly visible when looking through the air chamber.

Thanks. I do know how carbs work and have studied them intensively. I just cant be asked to fix them.

Need to determine if my plug fouling is caused by one of these factors:

valve seals are shot
Coil is shot
Something in the carb is shot

Two quick questions, what was / is wrong whith the carbs that made you feel you needed to buy another set.? and what grade plugs do you have that are sooting up?

WarrensKZ wrote:

hardrockminer wrote: These documents may be helpful in understanding how a carb works and how to rebuild them. Note that in the disassembly document he calls the diffuser a needle jet. I believe the needle jet actually sits up in the main jet chamber, and is partly visible when looking through the air chamber.

Thanks. I do know how carbs work and have studied them intensively. I just cant be asked to fix them.

Need to determine if my plug fouling is caused by one of these factors:

valve seals are shot
Coil is shot
Something in the carb is shot

You're welcome. I just assumed, based on your posts here (and on your thoughts on 29 mm carbs on a KZ650) that you didn't know much about carbs.

Always fun to mess around with your kids. Good luck with your fault finding.

Warren3200gt wrote: Two quick questions, what was / is wrong whith the carbs that made you feel you needed to buy another set.? and what grade plugs do you have that are sooting up?

I use ngk b7es

What lead me to believe there was a carb issue is, my son rode the bike about a week after I decided to get it ready for summer.

Cylinder 1 wasnt firing at all, so we changed the plugs and it was fine. My son also dithered with the hose connections.

Then we noticed the are around the baffle was covered in soot, which means its rich, and the plugs keep doing this. My neighbor, who was supposed to come round but didnt, told me he could smell fuel shortly after my son rode by his house. It was probably not a good idea to go buy a new rack of carbs, but here we are.

Does anyone have a diagram of the hose connections to KZ650 VM24s? Perhaps my son didnt hook it up properly?

Thanks gentlemen.

Ok, b7es is the correct heat plug, I prefer nippon denso equivalents but thats just personal preference.
Regarding a sooty baffle, that is normal even if your carbs are tuned in perfectly and have perfect plug colour, and is especially evident on 4 into 1's.
Going back to basics, with a oem airbox, stock jets and needles in the 4th slot with a delkevic your existing carbs should be eminently set upable with a fairly simple float height test, a colourtune for the the mixture, and a running vacuum sync.
Go through your carbs and confirm each of the above one a a time. You need to be systematic with these carb and bike set ups. Whatever you do to one carb will have an effect on all four carbs and cylinders performance.
Ignore your kids enthusiasm, many a bikes performance has been ruined by youthful desire to meddle.
Just swopping out for a different set of carbs will not fix anything and is the costly way to play it. Even if the second set ran perfectly on another bike does not mean they will run perfectly on yours. They need to be set up to match your bike and your bike alone. The condition of you engines compression and ability to create a vacuum for sucking in fuel coupled with your specific vavle and port cleanlyness all affect the performance of the fitted carbs.
So step 1. Confirm airbox y/n?
2, stock jets, y/n, if no what size are they?
3, wet test the bowl fuel heights and adjust as required,
4, set the air/fuel mixture screw to 1 . 5 turns out from lightly seated, these will be fine tuned with a colourtune when running.
5, Bench sync and when running vacuum sync them.

Things like valve guide seals can be semi checked by removing the exhaust and seeing if there is any oil evident in the exhaust port.

Not sure what your asking re hose connections.? Vacuum fed vm24's only have 1 fuel inlet to the bank which is in the middle of the bank between carb 2 and 3. Then there are two vent pipes which are located on the same level as the fuel inlet pipe but are located between carb 1 and 2 and the other is between carbs 3 and 4. These 2 are vents and should not be sealed or connected to each other. Ideally they should both be run up higher than the carb bank or even fed back into the airbox top hole.
The only other tubes are the 4 x overflow tubes located at the bottom of the float bowls.

Warren3200gt wrote: Ok, b7es is the correct heat plug, I prefer nippon denso equivalents but thats just personal preference.
Regarding a sooty baffle, that is normal even if your carbs are tuned in perfectly and have perfect plug colour, and is especially evident on 4 into 1's.
Going back to basics, with a oem airbox, stock jets and needles in the 4th slot with a delkevic your existing carbs should be eminently set upable with a fairly simple float height test, a colourtune for the the mixture, and a running vacuum sync.
Go through your carbs and confirm each of the above one a a time. You need to be systematic with these carb and bike set ups. Whatever you do to one carb will have an effect on all four carbs and cylinders performance.
Ignore your kids enthusiasm, many a bikes performance has been ruined by youthful desire to meddle.
Just swopping out for a different set of carbs will not fix anything and is the costly way to play it. Even if the second set ran perfectly on another bike does not mean they will run perfectly on yours. They need to be set up to match your bike and your bike alone. The condition of you engines compression and ability to create a vacuum for sucking in fuel coupled with your specific vavle and port cleanlyness all affect the performance of the fitted carbs.
So step 1. Confirm airbox y/n?
2, stock jets, y/n, if no what size are they?
3, wet test the bowl fuel heights and adjust as required,
4, set the air/fuel mixture screw to 1 . 5 turns out from lightly seated, these will be fine tuned with a colourtune when running.
5, Bench sync and when running vacuum sync them.

Things like valve guide seals can be semi checked by removing the exhaust and seeing if there is any oil evident in the exhaust port.

Not sure what your asking re hose connections.? Vacuum fed vm24's only have 1 fuel inlet to the bank which is in the middle of the bank between carb 2 and 3. Then there are two vent pipes which are located on the same level as the fuel inlet pipe but are located between carb 1 and 2 and the other is between carbs 3 and 4. These 2 are vents and should not be sealed or connected to each other. Ideally they should both be run up higher than the carb bank or even fed back into the airbox top hole.
The only other tubes are the 4 x overflow tubes located at the bottom of the float bowls.

Annoyed I just wasted $500 on the new rack. But anywhooo

So step 1. Confirm airbox y/n? Yes stock airbox
2, stock jets, y/n, if no what size are they? stock jetting
3, wet test the bowl fuel heights and adjust as required, will do
4, set the air/fuel mixture screw to 1 . 5 turns out from lightly seated, these will be fine tuned with a colourtune when running. yes sir will do
5, Bench sync and when running vacuum sync them. annoyed because a bench sync was done a month ago and all seemed well. not sure what could have cause things to go off.

what say you about getting the dynatek coil? Previous owner upgraded to Dyna S but kept the rinky dink old coils. I wonder if a bad coil could be fouling cylinder 1-2 even though 1 coil handles 1-4 and the other 2 and 3?

coils are testable with an ohm meter. Sometimes they can have problems when they heat up though. Maybe do a cold and a hot check? I don't know the values the primary and secondary coils should be at.

M_a_t_t wrote: coils are testable with an ohm meter. Sometimes they can have problems when they heat up though. Maybe do a cold and a hot check? I don't know the values the primary and secondary coils should be at.

Thanks Matt.

ive decided to replace them (not throwing money at the problem, just finishing that the PO started) to have continuity on the bike. If it has Dyna S ignition it may as well have Dyna coils. Not to expensive either. $125

The coils are a good idea. 30-40 year old coils are iffy at best. If one is weak it can make the bike run off and effect the overall performance. If nothing else, it would be one less thing to worry about.
Miller told me years ago, "If you don't want to cure the oil burning issue then maybe you should run two stroke oil and be done with it."
Steve

Putting on the dyna coils wont hurt and may improve things but its unlikely what is causing the sooted plugs.
As you say 1 and 4 are one coil, 2 and 3 is the other so to have 1 and 2 gone bad it would mean both your existing coils are trashed which is unlikely.
As they were bench syn'd a month ago unless anyone has had them apart since they will be close enough to do a running vacuum sync once the float heights have been confirmed. When you do a running vacuum sync I think you will be surprised how much you need to adjust them to get them all even. You also need to do them a couple of times as any adjustment you make will affect ones you have allready done. So each time you do them they will get closer and closer to where they need to be.
I suspect your float heights on the ones that are sooting is way too high causing a rich mixture on those cylinders.
I cant stress enough how you need to be systematic in your approach to these carbs. Everything needs to be right for them to run correctly. Once it is they are very smooth and responsive carbs.

Warren3200gt wrote: Putting on the dyna coils wont hurt and may improve things but its unlikely what is causing the sooted plugs.
As you say 1 and 4 are one coil, 2 and 3 is the other so to have 1 and 2 gone bad it would mean both your existing coils are trashed which is unlikely.
As they were bench syn'd a month ago unless anyone has had them apart since they will be close enough to do a running vacuum sync once the float heights have been confirmed. When you do a running vacuum sync I think you will be surprised how much you need to adjust them to get them all even. You also need to do them a couple of times as any adjustment you make will affect ones you have allready done. So each time you do them they will get closer and closer to where they need to be.
I suspect your float heights on the ones that are sooting is way too high causing a rich mixture on those cylinders.
I cant stress enough how you need to be systematic in your approach to these carbs. Everything needs to be right for them to run correctly. Once it is they are very smooth and responsive carbs.

Im sure.

But why would three float heights all of a sudden fall out of order, unless the kickstand has something to do with that?

Anyways, Im off to buy new plugs. I will pull the old four and post them.

Try a hotter set.
Steve