Noob vs. Mikuni VM carbs: Questions

Corrected; deadchef is right, looks like a stock 81-83 TCI box. Basic timing check and you should be good there. While the slide type carbs aren't supposed to be as fussy as CV carbs those don't look like very big, good quality pods.

I don't see an engine breather tube. Is there one? maybe your oil mess?

Heads up; I don't know squat about VM carbs!
 
gggGary said:
I haven't used one but yes that looks like it might be a Boyer Bransden (sp) electronic ignition. IIRC it triggers off the crankshaft (look in the LH round cover) and has an electronic advance. Basic timing check and you should be good there. While the slide type carbs aren't supposed to be as fussy as CV carbs those don't look like very big, good quality pods.

I don't see an engine breather tube. Is there one? maybe your oil mess?

Heads up; I don't know squat about VM carbs!
Click to expand...

isn't that a stock tci?
 
You could be right. On a 75?? But that can be done. What's the engine serial number? under front right engine mount.
Either case if it has fat spark and basic timing is good, should be no issues.
 
One look at the pods tells me those carbs came in a kit from sportingforless.com or one of its clones. Sometimes they'll send out a set with decent baseline jetting, but more often they skimp and send 'em out with a lot of generic crap in place, so you can't trust even one piece of brass in the carbs to be right except for the slides and float valves.

I've already written this shit up more times than I can count, and I'm not doing it again. Go to www.xs650temp.proboards.com , register, sign in, and access the VM section of the Carb Guide. You'll find baselines and procedures. One thing I will repeat is the strong recommendation to buy the Sudco Mikuni Tuning Manual and read till it makes sense. Yeah, there's a Mikuni tuning guide you can download free, but it doesn't have nearly as much on diagnostics. Good luck.
 
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I did go out and buy the tuning manual. I need to read it a few more times. Time goes by and the information gets lost in my head. Ill also read that info on the forum. One thing I don't understand about the carbs is the jetting. How can you tell if you need a different jet if your not sure the problem your having isn't coming from an idle adjustment or a combination of bad adjustments. I guess I'll find my answer while reading through all the literature. That's one questions that's been irking my OCD.
 
The site is down. I guess they've been booed away lol. Well none of the brass is right now because I got in there and changed everything 100 times over trying to get the bike running right. I might eventually pull them off and try my hand at the stock carbs before I mess with these any more. Have to do engine maintenance first. Where would be a good place to buy a new set of stock carbs or rebuilt carbs? I've seen some on ebay recently
 
In between and slightly above the intake manifolds.
A molded box shape with one or two nipples(depending).
The hose connects to the nipple/s and is routed back to the air boxes.
 
So this is a nipple right a over the carbs. At the top of the engine right? Should that have a hose on it or something like that? It shoots out hot air when I have the engine running. Took me a while to figure out what it was. I could feel it shootinh oit air when I stuck my hand down there to pop up the chokes on my carbs.
 
Yes the nipple is there for a hose. If the stock air boxes are removed some run a hose with a little pod filter. Some put the brake line check valve on the end to reduce crank case pressure. Some use Mikes reed valve. Some just run the hose to drain over the chain. Without any hose the oil mist is blowing on your carbs and top back of the motor.
Not a big deal I guess but it may be oiling your tire also. That would be my concern IF it were mine.
 
Ok good to know. So I can get away with sticking any hose on there without worrying about restricting the air coming out of there then I guess
 
Ok, so I got a parts bike the other day. Have been trying to figure out what year the new bike was. I did a second go on checking the year on the bike bike we have been taking about. I looked at the motor this time and it seems I have an 81 motor on a 75 frame. Did the 80's do points?
 
The motor number was the same as the frame number, if it's different, use the chart to see what year the motor is. Motor number is stamped vertical behind the right front motor mount a bit behind the tach cable boss. The parts mix and match pretty well so you can see a lot of different years of parts bolted together into one motor.
 
I realize now that my motor is an 81. My title says 75. We were talking a few weeks ago trying to determine weather the bike was a pints bike or not.
 
Ok just did the cam chain guide adjustment and valve adjustment. Found a video on Youtube, I just need to check to make sure the clearances he mentioned are correct. Need to chech timing and get new plugs as mine look like they were burnt to death with carbon. Anyone know where I can get a cheapish but reliable timing gun? Then on to the carbs!
 
Ok guys, I figured out earlier that I have a 80-81 xs650H. I checked the Cam Tensioner and I'm flush. I set the valves. I checked my spark plugs and they were completely covered in carbon deposits and the gap was way to tight so I got new plugs and set the gap correctly. Went out yesterday and bought a timing gun. I have no idea how to use it so I'll read up and figure that out tonight. So I kicked the bike after the adjustments that I made and nothing as usual. Had to give the carbs a squirt of engine starter and it started right up. So I think the carbs might be jetter wrong or they arent set up right. After I figure out the timing I'm going to look at grizld1's jet setting and see where mine are at. But as you can see in this video the bike appears to be idling smoothly. Once I pull up the butterfly's it wants to go crazy. I pop them down again and seems good to go. What do you guys think? As far as the bike racing, I checked the tuning manual for the vms and that could be a sign of a rich or a lean engine.

 

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