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Author Topic: Yamaha hs1 90cc twin clean up  (Read 7262 times)

Online irk miller

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Re: Yamaha hs1 90cc twin clean up
« Reply #10 on: Jun 12, 2016, 20:45:04 »
From what I could imagine it would allow more mixture(rich)into the engine w/ the same amount of air at full throttle..
You do that on the other side of the slide.  You can file away the bottom of the slide to take some of the angle away or flatten the arc to richen them up.  What's confusing is it's the top of the slide.

Offline stroker crazy

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Re: Yamaha hs1 90cc twin clean up
« Reply #11 on: Jun 12, 2016, 21:37:20 »
A little treasure hurco!

(I can't imagine what that carb mod is about)

Crazy
“Ride like the Wind” W.H.

Online Hurco550

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Re: Yamaha hs1 90cc twin clean up
« Reply #12 on: Jun 12, 2016, 21:44:48 »
So far Noone can explain the carb mod lol it will be interesting to see what the p.o. has to say.
"If you just picked up a drug habbit instead of a kawasaki triple at least you could get high while you waste money"
~ bradj
1988 tw200, the swamp donkey: http://www.dotheton.com/forum/index.php?topic=75455.0
2006 Suzuki DR650 Adventure monowheel trailer build: http://www.dotheton.com/forum/index.php?topic=75033.0
1976 BMW R90/6 farkilitious: http://www.dotheton.com/forum/index.php?topic=74349.msg882477#msg882477
1975 RD350 Road Racer: http://www.dotheton.com/forum/index.php?topic=70652.msg833688#msg833688
1976 GT250 Rebuild: http://www.dotheton.com/forum/index.php?topic=64973.new#new
Full Custom Pit Bike: http://www.dotheton.com/forum/index.php?topic=66954.new#new
1971 Yamaha 90cc twin HS1: http://www.dotheton.com/forum/index.php?topic=70498.0
"much ingenuity with a little money is more profitable and amusing than much money without ingenuity" - Arnold Bennet

Online irk miller

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Re: Yamaha hs1 90cc twin clean up
« Reply #13 on: Jun 12, 2016, 21:53:09 »
So far Noone can explain the carb mod lol it will be interesting to see what the p.o. has to say.
I've been googling the hell out this since you brought it up.  It's taken me to some sled forums.  They talk a lot about cutting the springs and drilling the slide to quicken throttle response.  I wonder if he was going for something like that?

Online Hurco550

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Re: Yamaha hs1 90cc twin clean up
« Reply #14 on: Jun 12, 2016, 22:14:47 »
I've been googling the hell out this since you brought it up.  It's taken me to some sled forums.  They talk a lot about cutting the springs and drilling the slide to quicken throttle response.  I wonder if he was going for something like that?
May have been what they were going for, but I still think it may be an uneducated attempt to get the slides to open farther thus "increasing power". Once the new ones come in, I'll see if at full open they clear the through hole in the carb. Also, I have a service manual on the way. Sometimes they sent some weird service bulletins to the dealers, and it could have been a service mod taken to far lol
"If you just picked up a drug habbit instead of a kawasaki triple at least you could get high while you waste money"
~ bradj
1988 tw200, the swamp donkey: http://www.dotheton.com/forum/index.php?topic=75455.0
2006 Suzuki DR650 Adventure monowheel trailer build: http://www.dotheton.com/forum/index.php?topic=75033.0
1976 BMW R90/6 farkilitious: http://www.dotheton.com/forum/index.php?topic=74349.msg882477#msg882477
1975 RD350 Road Racer: http://www.dotheton.com/forum/index.php?topic=70652.msg833688#msg833688
1976 GT250 Rebuild: http://www.dotheton.com/forum/index.php?topic=64973.new#new
Full Custom Pit Bike: http://www.dotheton.com/forum/index.php?topic=66954.new#new
1971 Yamaha 90cc twin HS1: http://www.dotheton.com/forum/index.php?topic=70498.0
"much ingenuity with a little money is more profitable and amusing than much money without ingenuity" - Arnold Bennet

Offline Shoeman

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Re: Yamaha hs1 90cc twin clean up
« Reply #15 on: Jun 13, 2016, 07:08:13 »
What size are those carbs?  I think I have a set of 26's of that type but that may be too big.   
I like cilp-ons, clubman's and superbike bars depending on the bike.  And rear-sets.

Online Hurco550

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Re: Yamaha hs1 90cc twin clean up
« Reply #16 on: Jun 13, 2016, 09:30:25 »
What size are those carbs?  I think I have a set of 26's of that type but that may be too big.
Thanks, but these are tiny. Vm16. I appreciate the offer though!
« Last Edit: Jun 13, 2016, 14:50:40 by hurco550 »
"If you just picked up a drug habbit instead of a kawasaki triple at least you could get high while you waste money"
~ bradj
1988 tw200, the swamp donkey: http://www.dotheton.com/forum/index.php?topic=75455.0
2006 Suzuki DR650 Adventure monowheel trailer build: http://www.dotheton.com/forum/index.php?topic=75033.0
1976 BMW R90/6 farkilitious: http://www.dotheton.com/forum/index.php?topic=74349.msg882477#msg882477
1975 RD350 Road Racer: http://www.dotheton.com/forum/index.php?topic=70652.msg833688#msg833688
1976 GT250 Rebuild: http://www.dotheton.com/forum/index.php?topic=64973.new#new
Full Custom Pit Bike: http://www.dotheton.com/forum/index.php?topic=66954.new#new
1971 Yamaha 90cc twin HS1: http://www.dotheton.com/forum/index.php?topic=70498.0
"much ingenuity with a little money is more profitable and amusing than much money without ingenuity" - Arnold Bennet

Offline jimmer

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Re: Yamaha hs1 90cc twin clean up
« Reply #17 on: Jun 13, 2016, 12:29:13 »
That is a sweet little bike! Nice find.
Yamaha Blaster Bike                                                                  Suzuki T500 Titan Twingle

Offline Shoeman

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    • My old RD tuning pages from the 90's
Re: Yamaha hs1 90cc twin clean up
« Reply #18 on: Jun 13, 2016, 19:48:14 »
If you're ever contemplating hot-rodding it a bit, I have the official Yamaha GYT tuning spec pages for the LS2, which shared the same basic layout and stroke, just up to a 38mm bore for 97cc displacement.  It gives factory porting specs, head info, and part numbers for the race bits, all long superseded and discontinued but still cool to see. 
I have a photocopy of the entire 1972 Yamaha Racing Tips publication.  Very cool stuff to nerds like me.

Geoff
I like cilp-ons, clubman's and superbike bars depending on the bike.  And rear-sets.

Online Hurco550

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Re: Yamaha hs1 90cc twin clean up
« Reply #19 on: Jun 16, 2016, 15:56:09 »
If you're ever contemplating hot-rodding it a bit, I have the official Yamaha GYT tuning spec pages for the LS2, which shared the same basic layout and stroke, just up to a 38mm bore for 97cc displacement.  It gives factory porting specs, head info, and part numbers for the race bits, all long superseded and discontinued but still cool to see. 
I have a photocopy of the entire 1972 Yamaha Racing Tips publication.  Very cool stuff to nerds like me.

Geoff
Wow, that's awesome! I enjoy reading through that kinda stuff to, but while my hands are on it, the plan is bone stock on this one. I am probably gonna sell it to fund another (bigger) Yamaha twin smoker.
"If you just picked up a drug habbit instead of a kawasaki triple at least you could get high while you waste money"
~ bradj
1988 tw200, the swamp donkey: http://www.dotheton.com/forum/index.php?topic=75455.0
2006 Suzuki DR650 Adventure monowheel trailer build: http://www.dotheton.com/forum/index.php?topic=75033.0
1976 BMW R90/6 farkilitious: http://www.dotheton.com/forum/index.php?topic=74349.msg882477#msg882477
1975 RD350 Road Racer: http://www.dotheton.com/forum/index.php?topic=70652.msg833688#msg833688
1976 GT250 Rebuild: http://www.dotheton.com/forum/index.php?topic=64973.new#new
Full Custom Pit Bike: http://www.dotheton.com/forum/index.php?topic=66954.new#new
1971 Yamaha 90cc twin HS1: http://www.dotheton.com/forum/index.php?topic=70498.0
"much ingenuity with a little money is more profitable and amusing than much money without ingenuity" - Arnold Bennet