Carbs - Carburetors

[Pyrobooster]

Click on "Tech" at top of page...............click on "Carb manuals'...........click on the first link. Lots to read, but read it all, maybe several times.When adjusting the mixture screw (with only 1 cylinder running), reduce the rpm as much as possible with the speed screw, so that you can detect a change in rpm.

I was just looking online for a more dummy proof way to sync my carbs once I get them all cleaned and back together.
I found a home made carb sync kit similar to this (http://www.powerchutes.com/manometer.asp).
Do you have any experience with a device like this, or know if it would work for a 1980 650, i think mikuni 34 carbs?

 

[Travis]

^ They work great on XS650s and any bike really.

All you need is about 12 ft of 3/16" i.d. clear hose, a yard stick or something similar, some zip ties or tape, and a couple of ounces of transmission fluid or oil. I don't use any restrictors or anything in the line and don't have a problem with the fluid jumping around too much.

http://www.xs650.com/forum/showthread.php?t=2317

 

[Pyrobooster]

^ They work great on XS650s and any bike really.

All you need is about 12 ft of 3/16" i.d. clear hose, a yard stick or something similar, some zip ties or tape, and a couple of ounces of transmission fluid or oil. I don't use any restrictors or anything in the line and don't have a problem with the fluid jumping around too much.

http://www.xs650.com/forum/showthread.php?t=2317

Where exactly do I need attach the tubes? I'm new to this. Also what is the process to balance them?

 

[XSLeo]

On the later bikes they have barbs in the carb holders that you hook the hoses to.
On some of the mid years the carbs had ports in the carbs, you remove the screws and install screw in barbs to hook the hoses to.
On the early carbs there was no way to hook the hose up, The sync procedure was based on the dead cylinder method.
Leo

 

[XSLeo]

Just recently found a guide to identifying the BS38 carbs. This tells the differences year to year but has fairly good pics showing the differences.
www.xs650.fi/pohja_files/fi/XS650carbs.htm It is a translation from Dutch, so some of the words, you have to think about a bit.
Leo

 

[leggers]

I reference the carb guide a lot so I made a cover for it... Thought I'd share

http://imgur.com/hDTbX

 

[Mitg]

Thank you Grizld1 (aka Dick Russell, Yamaha 650 Society
Tech Advisor),5twins, the Garage staff and all other routine contributors to this forum and thread. I have a 79 650 special which has seen better days. I was having problems with lack of power, missing and poor running at low rpms. I read all the recommended materials and followed the carb removal and cleaning step for step. Bingo, now running like a top. The bike ain't out of the woods yet but one major hurdle has been over come. Thank you all................and I am not mechanically inclined but the instructions and advice made me feel like I am. Thanks again!

 

[vdubplate]

Can anyone verify by this pic if these are Mikuni VM 34's by chnace?
Pay no attention to the notes.

I'm trying to adjust the idle adjustment but I haven't read through the manuals yet.

 

[vdubplate]

Hey here's the Suduco Mikuni tuning manual 4th edition. This isnt up anywhere for download so get it while the link is good. Link will die in 30 days

http://ge.tt/9MFagmH/v/0

 

[I am Carbon]

Hey here's the Suduco Mikuni tuning manual 4th edition. This isnt up anywhere for download so get it while the link is good. Link will die in 30 days

http://ge.tt/9MFagmH/v/0

cool thanks for the link vdub

 

[Underdog]

Can anyone verify by this pic if these are Mikuni VM 34's by chnace?
Pay no attention to the notes.

I'm trying to adjust the idle adjustment but I haven't read through the manuals yet.

the one on the left is your idle mix screw the one on the right is your slide stop or idle rpm screw...set both mix screws to 1.5 turns out from lightly bottomed out set the slide stop to just open the slide then a bit more be sure both sides are exact i use a drill bit to measre them from the back side with carbs removed but i dont have anything to sync them either...start the bike and warm it up make adjustments to both stop scerws equaly to get it to idle somewhat close fine tune idle mix screws for best idle both should be prety close set desired idle rpm with stop screws be sure they stay exactly the same recheck mix screws for best idle

 

[vdubplate]

I don't have a speedometer on my bike. If I wanted to check the rpm would it be as easy as buying a cheap one off ebay and screwing it into the side cover where the cable used to be?

 

[5twins]

Pretty much, yes. A tach is a valuable tuning aid, especially for getting idle speed correct. These bikes spec a 1200 RPM idle speed and they do need it. Run it much slower and the motor can just up and die at idle for no apparent reason.

 

[vdubplate]

Thats exactly the problem I have right now. The bike dies if its not fully warmed up. I might be ok if I get that tuned correctly.

 

[5twins]

These are old bikes and don't compensate for engine temp by varying the idle speed through electronics or a computer. You are the computer with these, lol. You have to find just the right setting so it will idle fast enough to not stall when cold but not too fast once it warms up. Took me most of my 1st season with the bike to do that. Even now, when still cold, I blip the throttle frequently at stops because I know it may just up and stall if I don't.

 

[vdubplate]

I was looking at tachs on ebay. They have a bunch of wires coming out. Is there one on the market for testing purposes I can plug into the side of my engine to get a reading or is that pipe dream?

 

[5twins]

If you want to connect it as originally done, you don't want an electronic one, you want a cable operated one.

 

[Underdog]

agreed a tach is valuable but if you dont have one and want to get bye adjust your idle high enough so it doesnt stall when warmed up and still shifts into gear without banging or going in hard of coarse with the clutch adjusted properly as well

 

[XSLeo]

Just get most any stock tach. Get a stock cable. Screw the cable to the engine and tach. Use this to set timing, idle speed, check alternator output, anything you need a tach to adjust. When done unscrew the cable from the engine.
Leo

 

[wilbur60]

Does anyone know why I cannot open the PDF's on my late model mac? I sure could use the manuals and the images. Just get a blank page when I open the site.