Yamaha SX 700 Vmax - Problem starting when warm - Snowmobile Forum: Your #1 Snowmobile Forum

cossie93 · 01-17-2012, 01:59 PM

Hi!

My 1997 Vmax 700 tripple is hard/impossible to start when it is warm.

When it is cold it start up in 1-2 pulls. And then it rides good.

When i have driven it a while and then stop and then imediately try to start it again, it doesnt start.

What I have done:
1. I have checked that I have a spark. (changed Stator this year to a new kimpex stator)
2. Fuel pump seems to work, I have disconnected one of the lines when it was warm and pulled. It comes out fuel. (I dont know how much it should come out from the line?). But could it be the pump? If the engine runs well should it not be enough fuel in the carburator bowl to start the engine?
3. Compression, top end. About 145psi on all three cylinders.
4. I have just inspected the Carburators, they look nice. I havent cleaned them yet.
5. It doesnt seem to get much fuel in the cylinders. The plugs isnt wet, even after serveral pulls with choke.

Any Ideas....

**RJ Gleason** · 01-17-2012, 03:05 PM

If you have not done a carb cleaning in a few years then it is likely past due for it.
It is possible that the floats are a bit too low so that there is not enough fuel for a warm start.

Will it start up if you "prime" the cylinders?

cossie93 · 01-17-2012, 04:32 PM

Quote:

Originally Posted by RJ Gleason

If you have not done a carb cleaning in a few years then it is likely past due for it.
It is possible that the floats are a bit too low so that there is not enough fuel for a warm start.

Will it start up if you "prime" the cylinders?

Ok, I havent tried that yet.
Just so I get it right.
Do I remove the sparkplugs, pour a teespoon of fuel in each cylinder, put the sparkplugs back, then i try again? with no choke.

PS. I bought the snowmobile last year so I haven any clue when they did a carb clean DS.

yamadad4 · 01-17-2012, 08:59 PM

its been my experience with most all yamaha two stroke sleds that they like just a bit of throttle on warm starts.(they dont like it on cold starts though) it will become second nature once you practice , give it a try. maybe an 1/8 to 1/4 throttle while pulling the rope, you will find the sweet spot.

my wife has actually figured out a trick although it makes me cringe watching her do it. due to her size she requires both hands for the rope pull so she flips the choke lever to the half position prior to pulling the cord then quickly flips it back.(this of course when i am not able to rush to her needs and start the darn thing for her)

dont rule out a good carb cleaning and confirm conditions and settings on the floats and seat seal, as well as the needle sealing. then try the throttle trick.

cossie93 · 01-18-2012, 03:48 PM

Quote:

Originally Posted by RJ Gleason

If you have not done a carb cleaning in a few years then it is likely past due for it.
It is possible that the floats are a bit too low so that there is not enough fuel for a warm start.

Will it start up if you "prime" the cylinders?

Hi!

I adjusted the floaters today, increased it about 2mm.
So far it seems to work
I did a 10 minutes run on the backyard and then tried to restart it again with no choke an no throttle. It started in second or third pull.

Now I can go out and try it a little more.

Thank you very much for your help.

I will keep this thread updated if I have the same problem again.

Best regards
Marcus / SWEDEN

cossie93 · 01-21-2012, 01:25 PM

Hi!

Tried it again today.
Same thing again, dont start when warm.

Im really lost on this.

Any more suggestions on troubleshooting ?

cossie93 · 01-22-2012, 05:50 PM

Hi!

Did a carb clean today.
Everything looked okay.
I adjusted the the fuel screw as specification in the workshop manual. 1,5 turn out from bottom.
Reed valves looked okay.

Started it and got it up to temp. Pulled strong from low to high. (as before)
But when I stoped , it was impossible to start again. (no choke)

Then I tried to choke it, After about 10 pulls i stopped. Pulled out plugs, and it was still quite dry. (shouldnt the plugs be wet after 10 pulls with choke?)

Is it possible that I have a crankcase leak when the engine gets warm?
And that is causing to little vacum to open the reed valves?

I will buy som starting gas and try to spray the lower end seals to see if engine revs.

Does anybody have any other suggestion?

**RJ Gleason** · 01-23-2012, 07:31 AM

Instead of giving it choke when warm, try starting it with the throttle cracked open a bit.

cossie93 · 01-23-2012, 11:00 AM

Quote:

Originally Posted by RJ Gleason

Instead of giving it choke when warm, try starting it with the throttle cracked open a bit.

I have tried that before, but no sucess..

yamadad4 · 01-23-2012, 07:24 PM

what did you set the floats at? all three were equal? are the choke cables set?

there were a few tech bulletins on those years back for hard starting issues, but most pertained to cold starts.

you may consider checking the pulse line to the crankcase as well as the fuel pumps output.

as i mentioned earlier, every yamaha i own likes about 1/8-1/4 throttle on warm starts, and i have lots of yamahas.

Captaincooter · 01-23-2012, 08:47 PM

from my experience when it will only start cold not warm it is 90% of the time your ignition coil. Heats up and expands. As long as its running you have continuity. When you shut down you lose that until it cools enough to contract again. It is very minute expansion and contration but is does occur.

richeyb3 · 02-06-2012, 09:32 PM

Quote:

Originally Posted by Captaincooter

from my experience when it will only start cold not warm it is 90% of the time your ignition coil. Heats up and expands. As long as its running you have continuity. When you shut down you lose that until it cools enough to contract again. It is very minute expansion and contration but is does occur.

Captiancooter--anymore info on the ignition coil heating and expanding? What are you looking for ? any fixes?
Richey

**RJ Gleason** · 02-07-2012, 07:13 AM

^^^^^^^^^^^^^
Yes, replace the coil pack.

yamadad4 · 02-07-2012, 07:19 AM

or change the caps first(cheaper) after clipping the wire back a little.

yes, they screw on and off and sometimes the wire connection corrodes to the point of limiting fire.

Captaincooter · 02-07-2012, 04:58 PM

Richeyb3- As the sled runs things warm up, with heat on most materials comes expansion. This expansion can can cause separation in the coils windings(bad coils). As long as its running you may arc across the windings and keep running. Once you shut down you may not be able to regain that arc of continuity until the coil cools and contracts enought to make contact.

yamadad4 · 02-07-2012, 06:57 PM

Quote:

Originally Posted by Captaincooter

Richeyb3- As the sled runs things warm up, with heat on most materials comes expansion. This expansion can can cause separation in the coils windings(bad coils). As long as its running you may arc across the windings and keep running. Once you shut down you may not be able to regain that arc of continuity until the coil cools and contracts enought to make contact.

well put! great explanation.

SRX 700 · 02-08-2012, 08:08 AM

Wait. He said he tested for spark already.

Captaincooter · 02-08-2012, 03:30 PM

Ahh yes I see. But did he check when warm or after the sled had some time to cool? Just going with my gut, and yes its a big one!

yamadad4 · 02-08-2012, 07:05 PM

Quote:

Originally Posted by SRX 700

Wait. He said he tested for spark already.

cooter is giving some good advise. at the moment that sled dies is when the spark test should be given. usually the best thing to do if your questioning the stators output. not that it is always the stator as there are other contributing factors but one does get a bit antsy when chasing electrical ghosts.

a stator than ohms correct at a given temp can lead you to a false positive, but from reading the symptoms given through the various posts, its hard to make an accurate keyboard diagnosis. the few given clues as to dry plugs after several pulls and the addition of an aftermarket vs oem stator(never had any luck with the cheap aftermarkets), the issue could be in several places.

carb cleaning is a rather general term. some think its as simple as spraying the outside and calling it clean. others are a bit more thorough and will actually clean every bit of a carb possible and make sure its clean. not implying in any way this is what the original poster may or may have not done, but i have properly recleaned carbs otherwise deemed as clean that werent.

SRX 700 · 02-08-2012, 07:49 PM

I am assuming he tested spark when the problem occured, as he tested the fuel pump when the problem occured (warm motor versus cold motor).

What do I know? Only cossie93 can confirm.