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Old 01-11-2011, 11:17 AM
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Default Need tuning help.... 87 Yamaha Exticer 570

Looking for some aaaassssistance! This is a continuation of this thread:
http://backcountryrebels.com/showthread.php?t=2177

I am helping a buddy get an 87 Exciter 570 back on the snow. He got the sled for nothing because there was no compression in one cylinder and it was in rough shape. After digging into the motor, I found 2 different sized pistons and some tough looking crank and bearings. I found a good motor which was cheaper than the parts to fix the existing one so last spring we dropped a few years newer 570 from an exciter in its place.

Still using the carbs (VM38 Mikuni 38mm) from the people who hosed the sled up to begin with, we just cant seem to get it running right. I found some diagrams that confirm the 300 jet (320 is factory, but seemed wawefully fat) is adequate. We have the idle screw out 5/8 turn and the air screw out anywhere from 1.5 to 2.5 turns out. (depending on what paperwork you look at)

Pilot jet is 42.5 per the specs
Needle clip position #3 per specs

I have dealt with many mikuni's but not one like this. It is calling for a #160 (Left carb) and #200 (right carb) "Power Air Jet" which looks to be in one of the openings in the throat of the carb where the air box mounts. There is nothing in there and the local shop was not helpful. There are no jets in those holes.

The sled seems to run decent above 4k or 5k rpms, but dies almost immediately anything under that. I tried to eliminate clutching as the issue by running it with out the belt and that did not make any difference.

any thoughts?
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Old 01-11-2011, 08:12 PM
snowdad4 snowdad4 is offline
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stare into the airbox side of the carb. 4 holes? one at 12 with brass, one at 4ish, another about 5(with brass) and last one at 6?
been awhile since i messed with those, havent had an exiter around for years. lets see where your at.
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Old 01-12-2011, 11:14 AM
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Thanks for the reply! I will get some detailed photos tonight and get them posted up. Your description sounds correct and according to the paperwork I have, it is calling for an air jet in the 6'o clock opening.

I'll get you some pics.

Really appreciate the help!
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Old 01-14-2011, 10:07 AM
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Ok dad... I have some info for you

Tunnel number is 82M
Block number is 88R
Cylinders are 82M
Head is 82M
Carbs are 84M

Choke (not really a choke, but a choke feature) cable is removed to eliminate
coolant tubes are plugged off
Jet in the port with the greenish/bluish hose (last picture)(power jet??) is a 1.5, but i think that is eliminated because the tubing just closes the circuit, right?


Not sure what that tells you.... but heres some pics of the carbs. no hole at noon, just 3, 5, 530, and 6 ish... 6 is the one I think should have an air jet in it and does not.
Attached Images
File Type: jpg P1010105.jpg (48.6 KB, 42 views)
File Type: jpg P1010107.jpg (48.6 KB, 42 views)
File Type: jpg P1010106.jpg (42.6 KB, 41 views)
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Old 01-17-2011, 05:37 AM
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Default yamaha

weston go to totallyamaha .com you can find specs and ask question best yamai site
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Old 01-17-2011, 05:39 AM
700redsled 700redsled is offline
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Default power jet

power jet is mid range fuel jei if I REMBER RIGHT FROM RACING DAYS WITH SRX,S
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Old 01-17-2011, 11:35 AM
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Thanks Don, Will give that a try also.
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Old 01-17-2011, 08:41 PM
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OK. Im pretty sure its the pto side crank seal. But it must be a very minor leak, which is why it ran decent last spring when the temp was warmer and now that the seal is cold and brittle....

It is a minor leak because carb cleaner was not enough to set it off, but ether was enough to leak through and notice it in the idle.

$30 part... will get one and see if thats it.
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Back Country Rebels - Forums > REBELS WITH A WRENCH > BRAND SPECIFIC TECH / DISCUSSION > YAMAHA

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