pops
New Member
Posts: 22
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Post by pops on Mar 18, 2024 14:28:42 GMT -5
I bought a non-runner last month and am in the process of bringing it back from the dead. I tore apart the carb to start cleaning and was dismayed at how varnished fuel had literally "glued" every sealing surface together. I literally had to tap a razor blade edge into each gap to gently separate each part. I'm in the process of soaking and cleaning all the parts now. My carb rebuild kit just showed up and I have a question for the collective brain trust here. Do you reuse your old brass jets or use the fresh ones in the kit? I've known lots of guys that would never use "that cheap Chinese sh*t" that comes with the kits, and insist on reusing original jets. Only problem is I don't have any idea of this bike's history, and whether the jets in the carb are original Mikuni quality.
Plan A is to just get the bike running and go from there. I noticed a receipt in the bike's manual that references a Wiseco piston. The bike also came to me sporting a Supertrapp pipe and a K&N filter in the air box. Should I expect the bike to run properly with a stock carb? What should I be on the lookout for once I get it running? I've read Ron Sutton's write-up about carb mods and am confident enough in my abilities that I could perform them if needed. I also know that there's a contingent out there that recommends chucking the stocker and fitting a new VM Mikuni, and although I will probably go in that direction eventually, I'd like to keep my expenses in check until I can verify I have a running reliable machine on my hands.
Okay brain trust, let's hear from you.
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neal
Junior Member
We may need a bigger hammer.
Posts: 34
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Post by neal on Mar 19, 2024 7:40:31 GMT -5
Hey Pops,
Just to clarify, is the stock carb in question a Mikuni VM34SS? Also who makes the repair kit you have?
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pops
New Member
Posts: 22
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Post by pops on Mar 19, 2024 8:00:45 GMT -5
Hey Neal,
I'm not sure...I understand that Yamaha used two Mikunis depending on year. What I just discovered is that mine has two square diaphragms on the bottom for the accelerator pump and the pump safety valve. I've seen pics of a triangular shaped diaphragm on the safety valve, and my rebuild kit came with the triangular part.
There's no name on my kit - it came from Amazon.
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Post by stevep on Mar 19, 2024 9:56:29 GMT -5
Slight concern in that your kit provides a triangular part where your carb needs a square piece. Other than that I would be tempted to lay out all the old/new parts side by side and make a list of jet sizes to see what differences there may be if you used all the new parts. The rebuild kit will or should give you a carb in standard trim. Your existing parts may be different on account of the different exhaust and air filter the bike now has.
From that perspective, you may find you need to keep some old carb parts if they will serve better with the new exhaust and filter. Generally original Mikuni parts may show the inscribed tiny square within a square marking, where space on the part allows.
Once I was forced to reuse original brass when the rebuild kit supplied a leaner pilot jet that just didn't work! I cursed myself for not listing the part sizes and comparing old with new first, before I commenced work as it took a day to find out. It was wrong of me to assume 'new must be correct'!
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pops
New Member
Posts: 22
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Post by pops on Mar 19, 2024 19:54:14 GMT -5
What a monstrosity! I've rebuilt plenty of carbs in my day, and have never had to deal with the complexity of what's on the bench right now. For such a simple bike, why in the world is this carb so bloody complex? I confess, my perspective may be a little off...the last carbs I dealt with were the Amals on my old Triumph (can't get much simpler). Thanks for your input guys. I am able to see the square markings on some of the parts Steve, so they'll just get cleaned up and reused. In the end, it looks like I'll only be utilizing the gaskets and o-rings, and a couple of the diaphragms from the rebuild kit. I see now why there's such a push in this community to just switch to the Mic VMs.  |
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Post by andy on Mar 20, 2024 3:31:42 GMT -5
What a monstrosity! I've rebuilt plenty of carbs in my day, and have never had to deal with the complexity of what's on the bench right now. For such a simple bike, why in the world is this carb so bloody complex? I confess, my perspective may be a little off...the last carbs I dealt with were the Amals on my old Triumph (can't get much simpler). Thanks for your input guys. I am able to see the square markings on some of the parts Steve, so they'll just get cleaned up and reused. In the end, it looks like I'll only be utilizing the gaskets and o-rings, and a couple of the diaphragms from the rebuild kit. I see now why there's such a push in this community to just switch to the Mic VMs. Pops, the OEM carb is okay if it’s in regular use and I wish you success with it. However my advice is be very careful how much time and money you throw at it, I know this from my experience and eventually I bit the bullet and bought a new vm34 and quite frankly once I’d got it dialled in I never looked back. If your in the states I reckon you will pick one up at a fair price. Plenty of help on the forum if you need any jetting help. Be lucky 👍. |
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neal
Junior Member
We may need a bigger hammer.
Posts: 34
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Post by neal on Mar 20, 2024 3:39:45 GMT -5
Andy is spot on. Wish I had gone that route before the expense (and considerable hassle) of sorting out my VM34SS. Horrible things.
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pops
New Member
Posts: 22
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Post by pops on Mar 20, 2024 8:17:13 GMT -5
Thanks guys! Trust me, not throwing any more $$ at this thing. I did find this in my research: www.ebay.com/itm/116012062148It's a Taiwanese copy specifically set up for the SR. Normally, I'd steer clear of something like this, but these guys are less than 2 hours from me so I can get a close look at their operation and maybe a ride on their SR. Plus they offer a 2 week money back guarantee if you're not satisfied for any reason. Unless anyone has any strenuous personal objection, I'd be willing to be a guinea pig and report back to the group. After all, knowledge is power. |
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Post by stevep on Mar 20, 2024 12:56:46 GMT -5
Reading other forums message boards on these, they're a Keihin copy and in more than one case I've read they came with genuine Keihin jets. At $130 it's not cheap, but if that's a real saving over and above what a Mikuni roundslide will cost then I'll leave it to you to judge whether it's worth experimenting with. Given the horror in pieces on your bench I may be tempted too! Let us know how it pans out.
Given the comments on cable length I'd be interested in their venhill cable options as well.
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Post by andy on Mar 20, 2024 13:52:39 GMT -5
Interested to see how it pans out.I'm trying to work out the throttle slide,it looks a bit of roundslide with a bit of flatslide  . Give it a go and perhaps the main concern is will it stay the course ? I would still shop around for mikuni vm's for the best price,I don't think there will be a great deal in it and if thats the case I would reccomend the mikuni...tried and tested plus stood the test of time. Very interesting,get back to us with the results . Andy |
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Post by gotsron on Mar 20, 2024 14:36:36 GMT -5
I'm a fan of wrecking yards and old dealership's spare parts rooms; I'm running VM 34 I got from a dismantler more than ten years ago that came off a CanAM 250 and 34Mm is probably fairly common size.
I was interested that in Germany (I read), guys were blanking off the various diaphragms on the VMSS carb and using it as a straight round slide carb. They must have access to more needles, slides and jets than I do though because mine was set up that way when I got it but ran really lean on the highway. I figured I needed to experiment with different slides, needle jets and slide needles but had no idea how to source them. The carb worked well up to about 60 mph.
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Petes2Wheels
Junior Member
Out riding the country roads
Posts: 91
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Post by Petes2Wheels on Apr 5, 2024 21:29:05 GMT -5
If it helps, get your hands on a cycleserv publications yamaha sr500 manual. It lists all the components, the markings, the levels and stock markings and settings of the carby. It is for the VM34ss. The tech specs show everything for rebuilding the carby. Awesome manual. Ask any questions and can get you the information
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pops
New Member
Posts: 22
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Post by pops on Apr 6, 2024 13:44:13 GMT -5
Thanks for all the input guys, I appreciate it. It tooks a few kicks (mostly to get the hang of the starting sequence...) but the bike's a runner now! I've confirmed the timing and tweaked the air/fuel mix screw so that it runs and revs well in the garage. It's nowhere near being able to venture outside the garage, but at least I know I can spend some $$$ on it with reasonable confidence. First up is replacing the painful drag bars, rebuilding the front braking system and researching tires. I'm going for a tracker/scrambler vibe since I'm too old for a cafe bike and I had a '79 stocker new when they were available here in the States. Guess I'll start another thread in the appropriate section.
Again, thanks for the corporate wisdom and encouragement!
Butch
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. Give it a go and perhaps the main concern is will it stay the course ? I would still shop around for mikuni vm's for the best price,I don't think there will be a great deal in it and if thats the case I would reccomend the mikuni...tried and tested plus stood the test of time. Very interesting,get back to us with the results .
