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Old 03-13-2013, 01:25 PM   #61
Kt-88
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Joined: Sep 2012
Location: SLC area, Utah
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Ordered new brass from Bill at Rocky Point. What a difference!!

For reference I have a 76 r90/6 with stock ignition and timing; nothing exceptional about the bike at all.

Vm32 carbs
30 idle
I80 main
6dh3 needles
158-O8 needle jet
Air screw 1 1/4 turn out

With this set up the top end is incredible. I just want to go fast.
Off idle is still just a bit rough, but only barely.

All I want to do is ride this around now.
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Old 03-13-2013, 01:44 PM   #62
oldroadie
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That's good info; you're needle jet is .005mm smaller than mine but the rest is the same (except the motor displacement but I can take that into account)...and I'm at 900 ft. while you must be in the 4000 ft. range. That gives a nice baseline to judge changes from. What groove did your jet needle end up in?
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Old 03-13-2013, 05:00 PM   #63
Kt-88
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Originally Posted by oldroadie View Post
That's good info; you're needle jet is .005mm smaller than mine but the rest is the same (except the motor displacement but I can take that into account)...and I'm at 900 ft. while you must be in the 4000 ft. range. That gives a nice baseline to judge changes from. What groove did your jet needle end up in?
Whoops. Forgot that bit! I put them in the middle to start with. Figured I would tune from there as necessary.
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Old 03-13-2013, 11:27 PM   #64
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Not to flood this post, but I'll relate my freeway riding tonight.

At the above mentioned settings and jetting, I can't redline 4th or 5th gear. First, second, and third feel pretty good, but WOT on the last two just never produced results. I mean, I was still doing 80 easily, but 2 k short and had ZERO acceleration capabilities. This leads me to think the mix is STILL rich on the main jet. I'll try lowering the needles tomorrow, and post results.
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Old 03-14-2013, 12:00 AM   #65
Houseoffubar
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Lowering the needles at wide open throttle has ZERO effect on top end jetting. If you want to lean the carbs (which sounds like the right direction) you need smaller main jets.
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Old 03-14-2013, 12:46 AM   #66
Kt-88
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Originally Posted by Houseoffubar View Post
Lowering the needles at wide open throttle has ZERO effect on top end jetting. If you want to lean the carbs (which sounds like the right direction) you need smaller main jets.
Bet you're right. Bill was stocked out of 180s so he sent 185s. ...probably need 175s here, anyway.
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Old 03-14-2013, 05:08 AM   #67
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Quote:
Originally Posted by Kt-88 View Post
Bet you're right. Bill was stocked out of 180s so he sent 185s. ...probably need 175s here, anyway.
That's what I'm running on my TM32's. 175 main.
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Old 03-14-2013, 05:47 AM   #68
oldroadie
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Originally Posted by Kt-88 View Post
Bet you're right. Bill was stocked out of 180s so he sent 185s. ...probably need 175s here, anyway.
You should be able to get those mains right off the shelf at the local YamaHonda dealer. I have a pair of 170s in hand you can have...I had to get sets of four since that's what the local supply chain minimum is but the cost was small so I didn't mind.
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Old 03-14-2013, 07:29 AM   #69
blaine.hale
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Lightly reading through this thread for encouragement.
What's to stop me from picking up standard Mikuni vm 34mm carbs for about $100 a piece and slaping them on the r90? I know I'll need proper jetting and cables, but what else comes in these mega expensive kits? Is it just the boots to fit to the existing BMW air filter?
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Old 03-14-2013, 07:46 AM   #70
hardwaregrrl
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Originally Posted by blaine.hale View Post
Lightly reading through this thread for encouragement.
What's to stop me from picking up standard Mikuni vm 34mm carbs for about $100 a piece and slaping them on the r90? I know I'll need proper jetting and cables, but what else comes in these mega expensive kits? Is it just the boots to fit to the existing BMW air filter?
Often times its cables as well. They're running 40$ for single or double pull. Obviously the single you would use the original cable to splitter, the custom splitter to the carb. They also come with a few main and pilot jets. Keep in mind Fred and I have a decent assortment if jets between us. Pilot main
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Old 03-14-2013, 07:48 AM   #71
Airhead Wrangler
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Quote:
Originally Posted by blaine.hale View Post
What's to stop me from picking up standard Mikuni vm 34mm carbs for about $100 a piece and slaping them on the r90? I know I'll need proper jetting and cables, but what else comes in these mega expensive kits? Is it just the boots to fit to the existing BMW air filter?
Not sure what comes in the mega expensive kits, but you'll need to make different cables - not too tough. I think ordering the carbs prejetted from Sudco with the right settings works out cheaper than buying the carb with "standard" jetting and then buying all the correct jets, slides, and needles separately. I ordered mine with cables from a guy on Amazon selling them prejetted for airheads. They were a LOT cheaper than the other sets available, but didn't come with rubbers. You're on your own there.
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Old 03-14-2013, 07:51 AM   #72
blaine.hale
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Quote:
Originally Posted by Airhead Wrangler View Post
Not sure what comes in the mega expensive kits, but you'll need to make different cables - not too tough. I think ordering the carbs prejetted from Sudco with the right settings works out cheaper than buying the carb with "standard" jetting and then buying all the correct jets, slides, and needles separately. I ordered mine with cables from a guy on Amazon selling them prejetted for airheads. They were a LOT cheaper than the other sets available, but didn't come with rubbers. You're on your own there.
If you ever stumble on that Amazon link again, I'd super appreciate a linky.

Sounds like there is zero point in buying a $400+ kit. Just buy 2 pre-jetted Mikunis and pick up the cables Jenna was talking about. My stock rubbers should work with mounting them up?

edit: this might be it. http://www.amazon.com/mikuni-34mm-ca...rds=bmw+mikuni

Looks like the same guy on this ebay set:
http://www.ebay.com/itm/New-Mikuni-V...188ac3&vxp=mtr
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blaine.hale screwed with this post 03-14-2013 at 07:56 AM
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Old 03-14-2013, 08:04 AM   #73
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Originally Posted by blaine.hale View Post
Yep, that's the guy. Looks like prices have gone up a bit though. Still the carbs prejetted from Sudco will run you about $150 a piece if I remember right, so with just the carbs you'd already be at $300. For $12 more this guy throws in the cables too (which aren't the greatest quality to be honest, but good enough). As for rubbers, your stock ones will work fine for the connection on the head, but you'll need to come up with something of your own for the connection on the airbox side.
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Old 03-14-2013, 08:22 AM   #74
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Rubbers can be found pretty cheaply at an Autozone. Measure what you need and then go to their assortment of radiator hoses. You can also do what I did (and I really like the result) is cut a long piece of rubber out of an old tire tube, and wrap the intersection between the carb and the BMW tube. You can pipe clamp the result, and it winds up being very water tight. My cylinders were under water for at least two minutes, and I was able to crank immediately once out.

I bought my first set from Rocky Point ... and the second set I got in a box of parts from a yardsale. Either way, I do have a few extra jets around ...

PS - In my opinion I would get the 32's for the R90. The 32's on the Dobber make the engine come alive. I had 34's on Greta ('78 R100) but I think I'me getting better performance out of the 32's on The Dobber.

Quote:
Originally Posted by Airhead Wrangler View Post
Yep, that's the guy. Looks like prices have gone up a bit though. Still the carbs prejetted from Sudco will run you about $150 a piece if I remember right, so with just the carbs you'd already be at $300. For $12 more this guy throws in the cables too (which aren't the greatest quality to be honest, but good enough). As for rubbers, your stock ones will work fine for the connection on the head, but you'll need to come up with something of your own for the connection on the airbox side.
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Old 03-14-2013, 09:16 AM   #75
blaine.hale
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Originally Posted by Beater View Post
PS - In my opinion I would get the 32's for the R90. The 32's on the Dobber make the engine come alive. I had 34's on Greta ('78 R100) but I think I'me getting better performance out of the 32's on The Dobber.
That brings up a good thought. Am I lazy enough to buy the pre-jetted 34 kit from this Amazon purchase or should hunt down some 32mm kit somewhere. Do you think it would be a big noticeable difference on the r90? I've seen a lot of people run the 34's on r75s.
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