MikesXS BS38 rebuild kit, main jet doesn't fit?

jjdalynh

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Ok, I've got 78-79 BS38s (AFAICT) and got the appropriate rebuild kit from mikesxs. Everything works but the main jets are slightly too big. Here's some pics to illustrate:
New on left obviously.
 

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You should check the needles for being the correct ones also. I have heard they could be the wrong ones. The jets might work if they screw in they are taller not sure if that matters.
 
Needles are correct (502). The thread pitch on the main jets looks the same, but they measure a little bit wider than the ones that came out.
 
Using anything other than genuine mikuni jets is at best a crap shoot.
If even the length is wrong what are the odds it will flow the correct amount of gas?
 
Seriously? Seems like you wouldn't keep sellng stuff that doesn't fit, or is there such variability in float bowls that some may fit and some may not?
 
The mains supplied in the kits are the proper kind, the N102/221 type, commonly referred to as a "small round" main .....

MainsCompared.png


What is wrong are the mains you found in your carbs. I can't be sure exactly what type they are, I'm guessing maybe they're what is referred to as just the "Round" type, 2nd from the right in this pic .....

MainJetStyles.jpg
 
Yeah, the ones that were in the bowls appear to be "round" type, so does that mean these are bowls from a different year or something? There is an "E" stamped in the bottom by the plug. Here's a pic of the bowls if that helps.
 

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All the BS38s used the small round type mains. If they won't fit in the bowls you have then I would guess those bowls came from some other bike model or have been modified (although they look like '78-'79 bowls from your pic). Have you tried fitting the kit mains and they just don't physically go in?
 
They drop in, but they don't screw in easy like the originals, here's the original measurment:
 

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I bought jets from mikes a few years ago for bs34s and the mains did not screw in2 the tube, they looked tge same but threads were def off.
 
The mains in your kit are knock-offs or copies. That might explain the "tight" fit. As Gary mentioned earlier, most of us prefer to use the real deal, genuine Mikuni jets (and floats, and float needles & seats). This aftermarket repro stuff is hit and miss, sometimes good sometimes not. If you have mods done to your bike like pipes and pods, you're going to need bigger than stock size mains and pilots anyway.
 
So its impossible to one stop shop for a complete carb rebuild kit? If so, whom would you go to for everything....orings, gaskets, etc.?
 
Not impossible, just not advisable. A lot of the generic parts work fine, some not so much, and (keystone I think) has been putting the wrong jets in some of their kits for years. Most of the kits have crap you don't need and not all the parts you DO need. unfortunately unless you have spare carbs it's a tear down, inspect, order parts, wait....... then reassemble process.

The ebay cruzin image BS34 kits seemed OK for gaskets etc. It came with an adjustable (groove and clip) jet needle and a needle jet that I haven't had the nerve to try. (yet)
 
Dont want to wait for inspection....been sitting in the rain for 6 years. I want to disassemble, soda blast and replace all the gaskets and orings and get larger main and pilots.....

I have found info on the butterfly orings....what else oring wise?
 
you got 34s or 38s? With sitting out in the rain you just gotta look first, they may not be salvageable. Southwest (dry, sand, more riding weather) bikes are much more likely to have worn out throttle shaft bores too. Worn out throttle shaft bores are pretty much a game over moment. Early 38's(71 for sure, not sure what year the bushings were added to the castings) don't have a bronze bushing insert and wear REALLY fast. I have a 71 with 10K and worn shaft bores, I have a plan, tools and some bushings but haven't "got R done" yet.
 
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