Vm29/cb750 dohc (I know.....)

Benz1991 wrote:

I ordered n100.604 117.5 and 110. The head of the jets are larger than the ones already in it but they have same size threads so I put the 117.5 and it didn't make any difference. Still sputters just off idle around ⅛ throttle. Anything higher it clears up and goes

 

Did you confirm the pilot/idle setting with a ColorTune kit? 1/8 throttle is air screw setting/pilot jet size.

From what I can find so far it is only ordered from over sea. Do you know where in America to order?

I order only genuine Mikuni jets on eBay or jetsRus.com. Are you sure you're not fighting that hole in the air screw? 
BTW EBC and other aftermarket jets are drilled differently. I tried EBC and the bike fell on it's face while trying to dial in jetting. 
Use only Mikuni for this reason. 

Benz1991 wrote:

From what I can find so far it is only ordered from over sea. Do you know where in America to order?

The kits are made by a company in the UK, just Google "Gunson" but they do have a web site and you can order direct. In the USA you can also order them on Ebay, not sure about Amazon but doubtful.

I inherited a kit from the 1970's but ended up ordering a new one to replace it about 8 years ago.

I was able to order the new one on Ebay for about $60 but they have to be more now. The 14mm one I have is #G4074 not sure what the spark plug is on a Honda head, probably 12mm not sure. The full kit has the "periscope" on the box.

You can even find used kits on Ebay or Ebay UK, more available on the UK site. As long as the glass is not cracked there is no issue with a used one. I sold my 1970's one when I got my new one.


 

its been a really busy winter but a few open garage door days and melting snow on our way!
i put color tune in and found blue flame at idle
pilot 17.5, 110  main and 4th needle clip
only has smooth idle around 1500
around 3000 flame is very bright orange
vac gauges on and all around 20-22" hg
changed needle clip to 2
now sync is way out. almost 40" and does not want to idle at all
what would cause #4 cylinder to have more vac than others after changing needle clip.
i am pretty sure the slides went back in as they should and bolts through throttle shaft were easy to thread in...

wrote:

its been a really busy winter but a few open garage door days and melting snow on our way!
i put color tune in and found blue flame at idle
pilot 17.5, 110  main and 4th needle clip
only has smooth idle around 1500
around 3000 flame is very bright orange
vac gauges on and all around 20-22" hg
changed needle clip to 2
now sync is way out. almost 40" and does not want to idle at all
what would cause #4 cylinder to have more vac than others after changing needle clip.
i am pretty sure the slides went back in as they should and bolts through throttle shaft were easy to thread in...



 

You have to remember that all these circuits are interconnected, you went too lean on the clip setting.

I would suggest putting clip back to #4 and investigate wet fuel level in the float bowl. You may be a bit rich on fuel level (orange on throttle) so maybe lower by 1-2 mm might help (not needle clip) Leaning the float bowl will lean all circuit (just like main jet size)

One thing you did not mention is how you performed this test. The engine needs to be at operating temp and is best done after a 20 min ride, then back to the garage and idling with a work shop fan running in front of the engine.

That 20's vacuum number seems acceptable to me.

Not sure why you had a crazy reading on one cylinder, it may have been a fluke. When you race the engine off idle it does some weird stuff in that transition from 1500 to 3000 (spark burn to catch up with extra fuel) Just be careful when using that glass insert at that elevated RPM because they can crack.

You need solid blue on idle not light blue (lean) There is all kinds of info on using a ColorTune out there, plus the instructions.
 

i got all the float levels adjusted to 4mm lower than gasket flange at the front of the bowl for the outside cylinders and i thought i should have the centers a bit higher so they are around 2mm lower.it does run sooo much better. color tune verified got rid of the rich spot off idle but idle hangs high after snap then slowly comes down. air screws are around half turn out. fresh plugs are still clean after 10 minutes of run time. does not like to idle lower than 1300 rpm, i would like it around 1000.
the needle clip is still #2. do you think that would help putting it back to #3? or larger pilot? 20 right now.

i forgot to say thanks again to all the suggestions and recommendations. its good to see progress coming out of it.