A cardinal sin of carburetors

[Caleb Hurst]

No problems here! Just a quick story about my carbs

So my carbs broke AGAIN recently on my 1981 XS650. I had the stock bs34 carbs. They ran like crap pretty much no matter what I did to them.

a few days ago they bit the dust for good. Could they have been fixed? Probably, but I was tired of tinkering with them. They were in need of replacement probably the day I got it.

Long story short after some research I decided to take a gamble on some super cheap carbs on amazon like DIRT cheap. To be specific JFG racing carbs 34mm. I installed them with 45 pilot and a 40 main jet. And guess what... fired right up, ran better than my bs34s. Most likely user error on the bs34s.

Don’t get me wrong the bs34s are superior, however mine were in such poor condition when I received the bike so this ended up being a better option for me.

would correctly tuned bs34s work better? Yes

would vm34s work better?
Yes

did I keep this entire project under 100$?
Yes

maybe this can help someone later down the road that doesn’t quite have the money to redo all the carbs on their 650?
Or not

feel free to chime in on this. If I have made fatal errors here. I can take the heat!! Haha!!

 

[2XSive]

Only time and your own experience will tell. Sounds like it runs good and you're not out much if they don't work long term. If you're interested in selling the 34s, post up some pics. Someone including myself might be interested.

 

[2XSive]

One note of caution would be to put new plugs in and follow the tuning guidelines for reading plugs to make sure you don't run to lean.

 

[Caleb Hurst]

That’s a good thought 2xsive I’ll check the plugs and see what the coloration looks like. Feels like it’s running rich right now but I’ll double check

 

[copernicusdan]

I had thought of doing this, I run the carbs Mike's sells, these look very similar, considering their under 30, and Mike's price is like 350 I thought it might be an option if I ever have a problem, I know some people had issues with Mike's carbs, varied quality, wonder if these are better made
That being said ive run mine hard the past few years, haven't had to mess with them much, have wondered if puting uni foam on would improve, but they work, but I'm no great carb tuner

 

[Caleb Hurst]

After a few days with these things it’s still running good. They seem to want to accelerate a LOT when I had the bs34s it was pretty even through all the acceleration. These just kinda want to go go go if you know what I mean. Not necessarily a complaint but that’s just kinda how they are.

 

[2XSive]

Sounds like you might be onto a great/cheap alternative to other much more expensive flat slide carbs. I'm sure you already know this but the responsiveness you feel is the difference between flat slide vs cv diaphram carbs. Like on
the BS34 stock carbs, the diaphram is pulled upen as vacuum increases, which takes time and thus feels more "even", but with flatslides there is no waiting for the diaphragm. Instant response. Some struggle with that responsiveness as it can feel really twitchy and sensitive. Others love it especially in racing situations. I put a Mikuni flatslide pumper on my hopped up Harley. It performed well but ultimately I went back to the stock CV carb as it was a bit more street friendly, plus the air/fuel mixture will auto adjust to some extent to changes in atmospheric pressure due to changes in elevation, with the CV carbs.

 

[grizld1]

If what you start with is bad enough, just aboout anything will be an improvement. There are reasons for the low price of those knockoff carbs, and those reasons are not pretty.