Need more low end. 1990srv mod

Srv560

Srv560

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Joined
Mar 22, 2015
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216
Location
Lake barrington IL
I have a Srv 540. 40 over. Psi pipe and comet 108 clutch with red spring. Stock carb. Jetted wright. Have all the mid range and top end I need. It's a dog out of the hole. Don't want dual carbs. May be dual exhaust. Any cons about that. Any info would be great. Thanks.
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Srv560 said:
I have a Srv 540. 0.40" over. PSI single pipe and Comet-108 clutch with RED spring.
Stock carb. Jetted right.
Have all the mid range and top end I need.
It's a dog out of the hole.
Don't want dual carbs.
May be dual exhaust.
Any cons about that ?
Click to expand...
You will not get more low end power with Twin pipes.

The secret here is clutching and get a Mikuni VM-40 carb with UFO and maybe gearing down depending on what you have today.

Use the Polaris Series-10 clutch weights.
They have a much better curvature than Comet or Arctic Cat clutch weights.
 
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Thanks what's a UFO that comes in the carb kit? I have a 38 off a skidoo formula three cylinder. To small? Stock butterfly is a 44mm. Where would I get this kit and carb boot? Thanks again


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108 is the wrong clutch for that sled. It's an overdrive clutch and the SRV secondary isn't an overdrive secondary. The usual problem with proper belt adjustment is no top end. If you are good there you are probably to loose with the belt on the low end which will skunk bottom end.

I would either go with a 102 primary to match up with the stock secondary or go to a Phaser II secondary which is an overdrive secondary and get the belt adjusted correctly.

One other option is to mod the stock SRV secondary. Here is a thread at Vintage Vmax with links in it to discussion and mods to help the 108 work. The 540 Vmax and SRV share the same issues with 102 vs 108. Calibrations will be different but basic principals apply.


http://www.vintagevmax.com/vvforum3/viewtopic.php?f=2&t=1506&hilit=108+comet
opsled
 
Thanks the bets I lose. The 108 comet came off a 1985 vmax. I hear a lot of people do run the 108 on the Srv. I have to send u a picture of the secondary. It looks different then the ones I have seen on other stock Srv. This one has a Crome cover that covers front and back of secondary. Thanks again. I have been fighting this issue for a year.


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If you have an overdrive secondary,it will be 11'' in diameter. If not, I would do what opsled said and find one. Exciter II's and 94 vmax 5/600 had them as well as 92-95 Phazer II's. Also make sure your belt is flush with the top of the secondary. With a 108 and overdrive secondary run a 89L-17641-00-00 belt. Those "chrome covers" are windage plates. The idea is to eliminate drag from the spinning secondary. How much they actually help??... I really dont know.
 
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thanks for the info. Looks like I have to get a secondary. It makes cense now. Always had problems with the belt running low and no low end. I have Ask this question for about a year. No one never said you can't run a 108 with a stock srv secondary. My son bought the sled after I told him no. Then he was burning up belts. Now I have it. Are there numbers on this one in the photo.To tell me what it comes off of?


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Srv560

Regardless of which primary clutch you use, it must be adjusted with shims under the spyder to get the correct distance
between the belt and the primary clutch sheaves.
If you use both "SMALL" o.d. clutches use the Exciter-I drivebelt.
If you use both "BIG" o.d. clutches use the Exciter-II drivebelt.
Do not mix and match.
 
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I am going to look for a exciter secondary 11 inch with over drive so I can run the 108 comet on the Srv. You think that's the easiest way to fix it?


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X2 on what lasse said. Yep, It will be the easiest, least expensive and best way to help with your issues. I would guess your secondary is off an early Phazer II because of the windage plates. If you take off the plates there will be a number something like 80L cast into the clutch
 
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I never thought how important the secondary was. Like you said on the primary spider. I have the 108 comet with stock Srv belt 1106. I pulled the belt tight against one side of the clutch and stuck a feeler gauge in there I had 80 thousand of a inch play. They say you should only have 10 to 20 thousands of a inch. That's where you said I should shim the spinder.


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Srv560 said:
I never thought how important the secondary was. Like you said on the primary spider. I have the 108 comet with stock Srv belt 1106. I pulled the belt tight against one side of the clutch and stuck a feeler gauge in there I had 80 thousand of a inch play. They say you should only have 10 to 20 thousands of a inch. That's where you said I should shim the spinder.


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Click to expand...
If you run the Exciter II clutch and belt, you probably wont have to shim the spider. That belt will be around 1-1/4" wide where the belt you have is roughly 1-3/16" wide. Do yourself a favor when you buy a new belt and buy oem yamaha. They are the same price as most aftermarket belts, sometimes less expensive and fit consisantly better. 89L-17641-00-00
 
Here are some example of sleds that had Mikuni VM-40 carburetors from factory:

* Arctic Cat Wild Cat-700
* Arctic Cat ZR-700

* Ski-Doo Mach-1 670 ( 1991-1994 )
* Ski-Doo MXZ 583 ( 1996-1998 )
* Ski-Doo MXZ 670 ( 1996-1998 )
* Ski-Doo Formula-SS 670 ( 1995-1996 )
* Ski-Doo Formula-Z 583 ( 1996-1999 )
* Ski-Doo Formula-Z 670 ( 1998-1999 )
* Ski-Doo MXZ 600 ( 1999-2000 )
* Ski-Doo MXZ 700 ( 1999-2000 )
* Ski-Doo Formula-Z 600 ( 2000 )
* Ski-Doo Formula-Z 700 ( 2000 )
* Ski-Doo Formula DeLuxe 600 ( 2000 )
* Ski-Doo Formula DeLuxe 700 ( 2000 )
* Ski-Doo Summit 600 ( 1999-2000 )
* Ski-Doo Summit 700 ( 1999-2000 )

:2strokes:
 
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