mikuni 36 or 38? for 400

[LINDEMAN]

I am considering a mikuni carb for a 400 MX to race next year.Any experience or opinions?

 

[LINDEMAN]

Thanks John,this kind of info is exactly what I was hoping for.I have spent alot of time farting around with bings also.Particularly getting the needle to center in the needle jet when instslling the slide.Front end up on tailgate,fishing around through the idle screw hole,and oh yes the last resort air filter removal mess.I have pretty much decided to scrap the airbox anyway and use aclamp on or something to aid jetting.Im only going to use it for vintage mx.If its real muddy we cancel races because it would tear up the parking areas .And if it snows the commute through the colorado mountains keeps some racers home. Without the bulk of our core group we risk losing money.It will never be quite like the 70,s in Indiana out here in Co.Gene Ramsey in Casey Ill.knowes how to put on a mud race!Hold on I got myself all worked up thinking about mud.Thanks again and I will think awhile before I buy.

 

[mikey]

quote:
Thanks John,this kind of info is exactly what I was hoping for.I have spent alot of time farting around with bings also.Particularly getting the needle to center in the needle jet when instslling the slide.Front end up on tailgate,fishing around through the idle screw hole,and oh yes the last resort air filter removal mess.I have pretty much decided to scrap the airbox anyway and use aclamp on or something to aid jetting.Im only going to use it for vintage mx.If its real muddy we cancel races because it would tear up the parking areas .And if it snows the commute through the colorado mountains keeps some racers home. Without the bulk of our core group we risk losing money.It will never be quite like the 70,s in Indiana out here in Co.Gene Ramsey in Casey Ill.knowes how to put on a mud race!Hold on I got myself all worked up thinking about mud.Thanks again and I will think awhile before I buy.

 

 

[mikey]

oops again..always send before I type..re: Bing vs Mikuni..I have played back and forth with both on CZ's and pound for pound prefer the Bing. The main thing on the Bing is a good (non egg shaper) pilot jet and a nice round needle and they work flawless. I always remove the carb to put the slide in..easier to center the needle..re: jetting I found an old chart that compares bing jetting to Mikuni on 34 and 36mm carbs only,
and for 400cc bikes but it should get you close
Bing- 1 needle 3nd notch from lean position- 280-285 pilot jet, #1 Slide 40 pilot jet, 1.5 turns air screw,175-185 main
Mikuni- 6FJ Needle, 3rd notch from lean pos, 159 Q5 Needle Jet, 1.5 Slide, 35 Pilot Jet, 2.0 air jet, 310 Main jet
34mm Mikuni for a 250- 6DP Needle, 2nd pos. lean, 159 Q-5 Needle Jet, 2.5 slide, 35 pilot, 2.0 air jet, 1.5 turns air screw, 210 Main jet
Unfortunately there were no 36 mm specs on the mikuni for a 250 but the 36 specs should get it running ok..I used a 36mm Mikuni on a 380 CZ with these specs and it ran great..I just like the bing better. for what its worth.

quote:
Thanks John,this kind of info is exactly what I was hoping for.I have spent alot of time farting around with bings also.Particularly getting the needle to center in the needle jet when instslling the slide.Front end up on tailgate,fishing around through the idle screw hole,and oh yes the last resort air filter removal mess.I have pretty much decided to scrap the airbox anyway and use aclamp on or something to aid jetting.Im only going to use it for vintage mx.If its real muddy we cancel races because it would tear up the parking areas .And if it snows the commute through the colorado mountains keeps some racers home. Without the bulk of our core group we risk losing money.It will never be quite like the 70,s in Indiana out here in Co.Gene Ramsey in Casey Ill.knowes how to put on a mud race!Hold on I got myself all worked up thinking about mud.Thanks again and I will think awhile before I buy.

 

 

[mikey]

ps: if you can find an old  Sudco Mikuni Carb and Parts manual its a great help. They show all the old needles and jets and what is the steps of each which makes it easier to dial in since Mikuni made so many variations..I have one if you need some help!

 

[400gs6]

I have both 76 and 77400GS6s'.The 76 has a Bing and the 77 has a Lectron. The Lectron runs clean everywhere. Wht aren`t more people using Lectons?

 

[Chris Brown]

My 400 has the old bing, and it works great. I did have to go to a leaner main and replace the slide needle and it's jet. Bing agency was very helpful. Before, it would load up trying to climb trails in the mountains.

I had major problems with a Jackpinger with a Mikuni conversion, finally replaced the needle with a leaner one out of the Sudco book and it ran great. I bought the bike as a non runner, restoration core. I found out it had a new top end, so I guess the former owner(s) never did get it to run right.

The bing is so simple, but the Mikuni has a choke circuit that makes starting so much easier. Mine is hard to start, it's so lean when it's cold. Once it gets some heat in there it starts first kick every time.

Either carb will work fine, but it can be difficult to fine-tune one not specifically made for the bike.
Chris Brown
PS. My new WORKS shocks work great.

 

[john durrill]

LINDEMAN,
Your intake manifold should be a bolt on. Larry Perkins or Al Bunhner should have one if you want to go with the Bing. Bings are easy to tune as long as the parts can still be gotten. Ask Dwiegh Rudder or Rick Grant about Lectrons. Both use them and may know where you can get one that would work on the 400. You need the right needle for the lectron. Make sure you can get the right needle befor you get one.
John & Peter

 

[LINDEMAN]

Thanks everyone,I think im going to stick with the bing.I always had good performance with the lectrons,Excellent bottom end and fuel mileage but I dont think they are vintage leagal.Thanks again.Dave Lindeman