Need your help w tuning Mikuni 45mm carb please

[johnle712]

I mean to type mount.

 

[mleach72]

I have two question:
1 - first picture - is there a gasket go between the carb and that mount? There isnt one when i take off.

2 - second picture: should there be a cover on the upper nozzel/nipple at the back right side of the carb ?
View attachment 124824View attachment 124825

I've never used that kind air cleaner adapter, but it clamps around the carb spigot, so it should seal ok. Just make sure both mounting surfaces are clean.

Yes, that nipple should definitely have a cap on it. That is creating a major intake leak. It is probably messing up your idle mixture adjustment quite a bit. It should run better once you get a cap on it. There is a lower one below that one. It looks like it has a cap on it.

 

[johnle712]

Thank you.

 

[johnle712]

The accelerator pump really stuck so i have to drill it to pull it out. Surprise, there were no spring under neath it .
I just put in an order at Niche cycle for replacement parts. Im hoping it get here early next week.
Thanks Mleach72 and JS.

 

[mleach72]

The accelerator pump really stuck so i have to drill it to pull it out. Surprise, there were no spring under neath it .
I just put in an order at Niche cycle for replacement parts. Im hoping it get here early next week.
Thanks Mleach72 and JS.

No spring?! Man, the previous owner had that thing really messed up! A main jet that was way too small, a vacuum port missing a cap, and a nonfunctional accelerator pump. No wonder it was running rough without a squirt from the AP when you open the throttle. You will love the carb once you get the PO's screw-ups fixed.

 

[mleach72]

The accelerator pump really stuck so i have to drill it to pull it out. Surprise, there were no spring under neath it .
I just put in an order at Niche cycle for replacement parts. Im hoping it get here early next week.
Thanks Mleach72 and JS.

Here is another thing to check. Is this screw missing or is it just turned down into the carb where you can't see it? That screw adjusts how long the pump stroke lasts. I usually set it so it is flush with the top of the carb.

 

[johnle712]

Yeah.. i am missing that adjustment screw there. Would you happen to know what size it is Mleach72?

 

[mleach72]

Yeah.. i am missing that adjustment screw there. Would you happen to know what size it is Mleach72? View attachment 124934

I don't know what size it is. It's probably metric though. It's a headless screw with a slot in the top, so I doubt you are going to fund it in a hardware store. Here is the part from Niche.

Mikuni Accelerator Pump Adjustment Screw

Allows for adjustment of the accelerator pump lever on new and old style Mikuni HSR carburetors.

www.nichecycle.com

 

[johnle712]

Bike is idling good now. No more sneezing/ spitting or cutting. Running strong and smooth. Just a little pop on decel. Overall im pretty happy.

Thank you million sir Mleach72!!!!

Here is a few pics of my dogs. The one with air-brush has Mikuni carb. The other plain blue has super G carb.
Have a great week to all BigDog Bikers.