rwilkins
XS650 Member
Looking to get rid of my BS38 carbs, any good advice as to the best route in aftermarket carbs to go with?
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Best aftermarket carb fo a 77?
- Thread starter rwilkins
- Start date
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- Tags
- carburetors
If those BS38's are the stock 76-77 carb set, you have about the best of the BS38's. A little proper cleaning and tuning and your bike will run about the best it can.
Leo
Leo
rwilkins
XS650 Member
I think in the past someone has done some work on the idle mixture screw. The screw must gotten stuck and some one drilled it out and put a screw in the back side. Could this be the reason they are almost impossible to tune. Is there someone that anyone knows of to send them to, to rebuild them properly and sync them up? Ive done everything to my ability, I might need to send them to a pro.
Send them off to member oldskoolcarbs, check out his pictures. They are awesome!
Show us some pics of the screw you're referring to. I'm thinking you mean one of the idle speed or linkage screws, not a mix screw. If it is a mix screw and they drilled into the carb body, the screw's seat may be damaged which would make that carb beyond repair in most cases.
5twins, I'm pretty sure he has it right, it's the mix screw.
What happens is someone screws the mix screw in until the brass tip shears off and gets stuck in the carb body. So, you drill a hole in the body on the opposite side until you reach the air mix cavity, and push the nub back out.
I had a carb set with this problem, and this solution never occurred to me. So I sent it to an expert who will remain unnamed. He did the drill-out and really screwed it up. I was able to fix one body with much time and work, but the other was destroyed.
So, rwilkens, you probably have carbs that are beyond repair. If you want to send them to me, I'll see what I can do. Your other choice would be to try to buy two bodies off of this forum. Maybe from me. Or, buy a parts carb on eBay. I just got a nice ebay deal on a set of parts carbs that were all there except for the slides. People cannibalize the slides out of carb sets because slides with good diaphragms are valuable.
What happens is someone screws the mix screw in until the brass tip shears off and gets stuck in the carb body. So, you drill a hole in the body on the opposite side until you reach the air mix cavity, and push the nub back out.
I had a carb set with this problem, and this solution never occurred to me. So I sent it to an expert who will remain unnamed. He did the drill-out and really screwed it up. I was able to fix one body with much time and work, but the other was destroyed.
So, rwilkens, you probably have carbs that are beyond repair. If you want to send them to me, I'll see what I can do. Your other choice would be to try to buy two bodies off of this forum. Maybe from me. Or, buy a parts carb on eBay. I just got a nice ebay deal on a set of parts carbs that were all there except for the slides. People cannibalize the slides out of carb sets because slides with good diaphragms are valuable.
The man asked about aftermarket carbs not how you all feel about stock ones. If you ask Heiden tuning they'll tell you the 36mm Dellortos they sell make the most power out of the choices they have, but if you look at what racers were really running right before any given class switched to fuel injection it's always the same, flat slide accelerator pump carbs from Keihin or Mikuni. For a decade the FCR was pretty much "the carb". The last motocross bikes just stopped using them in 2010.
Sn34ky
Farmer's can build bike 2
I have a Keihin FCR 40mm from a MX Quad laying... do you guys think it can be runnable with a 2 into 1 intake on a stock 78 motor with baffled headers? Can I get a little improvement over stock 38s? Some low end gains and throttle response maybe?
itrguy
XS650 Addict
I run a mikuni vm36 with a 2 into 1 intake.... runs great!!!
Yes, you can run any year on either the BS38 or BS34 carbs. Just be aware that the first years had the carbs point out at an angle so any thimng other than the right carbs you can't use the stock air boxes. This also applies to swaping the later bBS38 with the BS34 carbs the BS34 carbs are a bit longer than the BS38 carbs so you need an after market air cleaner.
I have ran my 75 with the stock carbs and air box, the stock carbs with K&N pods and UNI-Filters. I have a set of 82 BS34 carbs on it now with UNI-Filters. Both carb sets run the best with the UNI-Filters. The BS38,s give a bit stronger WOT responce, but the BS34's have smoother responce across the board, this gives it slightly better drivability.
Leo
I have ran my 75 with the stock carbs and air box, the stock carbs with K&N pods and UNI-Filters. I have a set of 82 BS34 carbs on it now with UNI-Filters. Both carb sets run the best with the UNI-Filters. The BS38,s give a bit stronger WOT responce, but the BS34's have smoother responce across the board, this gives it slightly better drivability.
Leo
