belt engagement on 83 vmax - Snowmobile Forum: Your #1 Snowmobile Forum

red89notch · 02-24-2013, 02:05 PM

what rpm is the belt supposed to engage? mine doesnt engage until 4200. it idles at 1500

i thought it should engage at about 3000, also how to i adjust the engagement point>

thanks

yamadad4 · 02-24-2013, 04:45 PM

4200 is about right for that sled and full shift out should see around 8200.

to reduce the engagement, you need to figure out what spring is in there now and compare the specs for one with a lower pre-load. getting down to 3000 and keeping the top end may be a challenge.

edge800ves · 02-24-2013, 04:54 PM

^^What he said

But if it used to engage at 3k you may just need a new belt they get narrower as they wear and leave you with more of a sheave clearance!

red89notch · 02-24-2013, 08:02 PM

I was thinking that it should engage around 3k if it's engaging where it should be then I'm not going to mess with it. it has a new belt on it. I got the sled last year with only 200 miles and it sat for over 20 years in a shed, the carbs were emptied and the openings duct taped off. I changed plugs, cleaned out the oil reservoir and lines and put new oil in , and fixed the spark.plug wires and it fired up on the second or third pull.

the only other thing I want to check is the carb adjustment because when cold it does have a slight bog if u go full throttle from a dead stop, but after the sled has been running for about 30 min it goes away so I'm assuming that would be kinda normal, but I am not real knowledgeable with 2 stroke motors. also is the idle supposed to be about 1500?

also I know u shouldn't run it full throttle for a long time so I was wondering is 7-8k too much to cruise at?

thanks for the help and suggestions

**kccats** · 02-25-2013, 07:10 AM

At 3000 rpm the motor wont make enough hp to pull the sled!

yamadad4 · 02-25-2013, 09:22 PM

1500 at idle is right in there. you may bump it up to around 16 and see if the bog clears. your air screws should be between 1/4 and 1/2 turns out. dont overlook the clutches as a possible bog source, could be a bit rusty or corroded from sitting so long.

full shift at 8200 is where the power is on and you should be at full throttle. cruising at 7- 8000 is is pretty much pinned. ok if your running good fuel and jetted correctly if your doing long pulls, dont be afraid to pump the happy lever occasionally.

red89notch · 02-26-2013, 07:48 AM

I can cruise at 7-8k at about half throttle. well after I give it some.gas till about 8k and then the rpm drop to about 7 (without letting off the gas) I am assuming that is when the belt fully engages, when the rpms, then I let off the throttle to about half throttle and cruising at about 7k.

I'm a mechanic, a younger one so I didn't grow up working on carbs, lol. but I can tune a carb fairly good, the only problem that is frustrating is when I hook the evaccum gauge to the vaccun.port on top.of the carb the vacuum is anything.but close to being stable, so.it's more.difficult for me to tune it. I was thinking about just jacking the idle up to about 3k to get a more stable vacuum then tune the air/fuel screw, on a car I would adjust the screws at idle but a car carb the screws r only for idle mixture, not sure if the screws are for during throttle, or if the jets take over after off idle running.

thanks for the help

**RJ Gleason** · 02-26-2013, 10:56 AM

Turn the air screw in in 1/8 turn increments until the idle starts to rise and then sued the idle stop screw to set to desired rpm.
It's just that simple!!

red89notch · 02-26-2013, 03:07 PM

Quote:

Originally Posted by RJ Gleason

Turn the air screw in in 1/8 turn increments until the idle starts to rise and then sued the idle stop screw to set to desired rpm.
It's just that simple!!

it's got dual carbs and I would like to make sure that both carbs are tuned together that way one cyclinder isn't working harder then the other one.

**RJ Gleason** · 02-26-2013, 03:14 PM

Same procedure, just need to do it twice. [a little on each at a time]

yamadad4 · 02-26-2013, 08:06 PM

your better off tuning by ear and keeping the idle at the 1500 mark. as rj mentioned, but i will add a bit more detail, turn the screw in or out until the rpms rise. for me its more ear than tach, but whatever works for you. for some reason i do the mag side first. once you find the spot where the idle begins to increase, stop turning. at this point you want to reset the idle back to where you started and move to the next carb. i do one then the other.

once you have achieved your desired results, check the butterflies with the engine off to see if they are full open and equal. you may have to backtrack by adjusting the cables and then re adjusting the air screws. be sure you have some free play at the flipper.

once you think your there, a few test runs and checking the plug color will guide you from there.