Looking for NEW Carbs.....

Hi Guys

I'm new to the XS400 form, but not new to XS 400's.

I have an 82 Heritage Special, owned it for about 7 years, and it the second XS. First one was lost in a crash.. But i'm still here ...

Long Story Short- I've been battling Carb and Tuning Problems for almost 2 years... I keep rebuilding, cleaning, and tuning. And just can't get the thing to run right... Fast Idle as high as 3000rpm, Slow Idle, Running Rich, Running Lean. But it's never consistant...

Anyways i'm tired of cleaning and rebuilding and then tunning . Albeit I'm no mechanic, but i'm no slouch to a wrench.... I would LOVE a NEW set. Don't have to be stock, but if anyone knows of a replacement> I would Owe you big time.

I decided to completely mod my XS and build a CAFE RACER as so many of you have done.. Want something that will be reliable and run.....

Any help, thoughts, or oppions are greatly appreciated.

Thanks in advance.....

You have found a great place for info! and lots of Pic, you will have to add your to the mix! As you work though different parts you have to bounce between the manual, and stuff others have done before you. Find some one with pics in the albums and see if you can find there early posts, to see their trials and tribulations. Then the bottom of the comments will show you 5 similar post based on key words. Take it one step at a time. inbetween ordering and waiting for parts to arrive, Clean scour, paint, "Think twice, cut once" Sand, paint. be patient, HAVE FUN
Tobie

Swissbeats said:

..... Any help, thoughts, or oppions are greatly appreciated. Thanks in advance.....

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Hi Swissbeats, welcome to the Forum. I hope you get the help you need.
Assuming you are south of "60" and there's still some warm riding ahead, I do have a thought which might keep you going until your re-build starts.
Your intro mentions continual messing about with the carbs but you didn't mention if you had confirmed that there are no leaks in the air intakes. I have read a number of threads on here where a tiny crack in the boots makes the bike act inconsistently (to put it mildly).
One easy way to test for it is to spray carb cleaner (I think - or is it quick-start? - better check) on them when the engine is running. If there's a leak, it will get sucked in through the crack and will change the way the bike runs. If it happens, you need new or repaired boots, not new carbs.
Probably an erroneous thought - but a thought nonetheless.
Best of luck.

I can empathize with you. Last Summer I had a huge problem with the Yamaha Mikuni carbs. I even sent two pairs down to a chap in Florida who said he could rebuild them for 100 dollars each. Silly person that I am i believed him, and got carbs back that were waaay worse then they were when they left here. I finally did get them working, but they never did work as well as I had hoped they would. Then I discovered something really cool... Suzuki made a GS400 and GS450 from 1979 till 1984. Those Suzuki Mikuni carbs are different and have main and pilot jets in the float bowl rather then in the main body. The enriching mechanism is a lever action rather than a push/pull rod. The Suzuki GS400/450 Mikuni carbs in my opinion are waaaayyy better then the ones stock on the Yamahas. Also the idle mixture adjustment screws are on the side, so you don't have to remove the tank to fine tune. All in all a way better solution. They are commonly on Ebay for 30-75 bucks.

The spacing of the carbs are so close to the Yami that it is not a problem to slip them onto the Yamaha boots. The accelerator is similar and its easy peasy to install where the Yamaha carbs were. As far as jetting is concerned I found these variations of the Mikuni carbs to be very flexible as per pod filters, open exhaust etc. Also the flexibility from the Suzuki 450 to the Suzuki 400 and Yami 400 seems to be of no concern. I am able to bolt them on and go.

Give them a try if you want to replace the stock Yami carbs.

Mike...

Lou Ranger said:

... One easy way to test for it is to spray carb cleaner (I think - or is it quick-start? - better check) on them when the engine is running....

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i always use propane. if there's an intake leak then the RPMs will drop - the engine will sound like it's "bogging down". um... don't light it! hahaha.

welcome to the forum.

I've seen carbs on the bay jetted for xs650's but if your prepared to do more work, I'm sure you can get them to run.

No... I would not recommend using 650 carbs. I would think you would be entering a nightmare of jetting issues. The reason I suggested using the 1980 Suzuki GS400/450 Mikuni carbs is the fact I was able to run them as is. With no jetting changes. I just cleaned them And bolted them on. It ran very well. I went through all gears under all loads and I could not discern any problems at all. A much better carb than the Yamaha version of the Mikuni. And the idle jets are on the sides of the carbs rather than on the top, so the hassle of tuning with the tank off is solved. Plus I like the choke lever rather than the silly looking push/pull choke control on the Yamaha. I have seen no downside to this swap. The GS400 and GS450 are so close in carb requirements to the Yamaha, that no jet changes are needed. I also noticed no difference with pod filters, or free flowing exhaust. Or at least if it is different it did not affect performance under normal riding conditions. If you are into scraping your pegs on the road you might want to tune for performance. The bike starts easily without choke in 70 degree temps. Under cold conditions it is possible it might need a bit of choke.

The older gs400 carbs are just like the xs360 carbs with a few changes.

I'm running on the stock Mikunis on my 82 and they have been treating me very well since I rebuilt them. Things to check that could've been overlooked are checking the diaphragms for any rips or wear and making sure that the passages are clear, which can be checked by spraying carb cleaner in them and making sure that it is coming out the other end. Mine were totally clogged and one cylinder wasn't firing before the rebuild, and now the bike runs great!

No promises that these are going to work for you, but they were things that definitely helped me.

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Thanks for all the comments and suggestions. Think I will spend a bit more time searching for some "new ones".... And if all else fails, try a "professional" rebuild, and replace the intake "boots".....

I'll keep searching the forum, and post.

Expect to hear from me again.

Thanks Again!!!!!