I need help from the mass of knowledge here....

Y

YammyScoot

New member
Joined
Apr 5, 2018
Messages
9
Location
Seattle, WA
Hi,

I have been trying to diagnose an issue with my 2003 SX Viper Mtn out here in Seattle. Problem is, there are not many folks out here that ride Yamaha sleds, and the two strokes even less so. Therefore, its hard to diagnose and troubleshoot a strange issue (intermittent mid-range miss/burble) with anyone in person that has any experience with these sleds. I would describe it as not really a miss, as it never stumbles or anything when you nail the throttle....its has no issue coming up to 8800-8900 RPM, starts and idles great. I just installed an electric start and reverse kit...so I want to keep the sled butttttt........ keep in mind it only has 900 miles on it.....


- Compression numbers Mag 125, Ctr 125, PTO 115

- leakdown 7% across the board on cold engine

- never any error code flash

- I changed the coil pack with a known good used set.

- Pulled the wire harness from under the engine and it looked brand new under all the harness protection and tape....no issues found.

- Pulled the headlight harness and did the same...no issues found

- pulled carbs and cleaned very thoroughly......and I mean everything was spotless, all jets, passages, etc. Set float height to nominal....still has burble

- bought known set of different good running carbs ...still has burble

- pulled, cleaned, and calibrated power valves...still has burble

- pulled reeds, reed cages and verified closed at rest, no vacuum leaks....still has burble

- confirmed fuel pump to all carbs....still has burble

- changed spark plug caps....still has burble

- changed primary clutch to known good one.....500 miles on factory clutch.

YET TO DO:

- I have a new Yamaha stator to go on it....

- try a different CDI box

- another wire rub thru somewhere....CDI area looks to be ok.

- I have the original set of carbs that just confirmed the following
MJ - 150
PJ - 45
NJ position - 3
PS - 2-3/4

We mainly ride in the 2500 - 5000 ft elevation, temps 15 - 35


Next step is over a cliff I am....

Sleepless in Seattle Scott.......:o|:ban:
 
Well, from my limited knowledge on Vipers, the common problem was the needles were lean stock, and your problems seem to be in the mid range, which is what the needle controls. Have you tried them at 3.5?
 
x2 on needle setting. brother raised his on his 02 and my dads 05 sx venture with the same motor. having ridden my dads quite a bit last season, his gets all burbly when it gets loaded up from slower trail driving. when it gets like that, a good wot scream across a lake or on a straight usually cleans it right out.
 
Thanks Mr.Murder...lol

Yeah, I too had read lots about the mid-range lean condition and thought I should at least move up to 3.25 at a minimum. Riding in the PNW is almost always part throttle with very short full throttle blasts as there isn't much flat, straight ground to really wind them up on here.

I also switched over to non-ethanol premium fuel and wasn't sure if that contributed or helped the lean condition....so, still researching that as well.

I have a set of 55 pilot jets but, I am afraid that might be too much a jump.

Thanks again for your help and advice!

Scott
 
Pilots will effect right off idle, you need a needle adjustment. Pilots are good.
Ethanol fuel will make your problem worse, as it leans out the motor. It’s oxygenated fuel.
I would try raising the needle.

Oh, also, Mr. Murder is my father, you can just call me Murder.... Lol !
 
Ok then Murder it is....LOL.

As I am sitting here in the Galley (kitchen, to you land lubber folks) assembling carbs....I think I have read and researched enough, and with y'alls input...decided to go with a JN3.5 and stick with non-ethanol fuel. I never was really happy with the color of the plugs and always thought they were a little lean to begin with, so I'll go two jumps on the plugs and see if I can get some color in them and then back them off if they appear too rich. I've never had anything close to a fouled plug and would certainly feel better if I had. So my full setup I think I will try will be:

JN 3.5
MJ 150
PJ 45
PS 2-3/8 turns
also installing new needle and seat, setting to 13.2 mm nominal.

I certainly would appreciate any other feedback, advice, commentary, snide comments, or other cussing that might steer me in the right direction as this thing has me #$%&* baffled thus far!.....the snow is starting to fall this week in the mountains....tis time....:sled1:
 
They suggest 2 3/8 for your elevation ?
1 7/8 is stock.
And I think 3.25 should be enough on the needles upon further thought, especially at your elevation.
 
Yes, the sheet I am looking at says 2-3/8 for my approximate elevation and temperature....BUT, I also have slight smaller pilot jets.....so, my theory is that I could also try ethanol fuel to lean it out just a bit....if i still get the miss/burble.

In addition, I just ordered all the jets, pilot jets, etc to do whatever combo it takes.....I have another set of carbs to play with so I might just set those up at 3.25 with another jet combination as well. I am getting really good at changing the carb racks....lol.

Thanks for the advice again...Sir Murder

In the end, it is what I call a miss or burble that I am hearing. I have yet to "feel" a miss or stumble while riding but it is audible for sure. I am going on the assumption that it is a lean condition, that shows after the sled gets ridden awhile. I
 
Thanks "a couple of bucks"....

Can someone explain the difference between "Needle Jet" and "Jet Needle"?..:o| I am assuming one is the actual needle, and the other is the thingamajig the needle gozinta?

Scott
 
The needle sits in the Seat, which is like a jet, has a o-ring around the outer diameter. May want to make sure they haven't shrunk up on you as well.
 
YammyScoot said:
Thanks "a couple of bucks"....

Can someone explain the difference between "Needle Jet" and "Jet Needle"?..:o| I am assuming one is the actual needle, and the other is the thingamajig the needle gozinta?

Scott
Click to expand...

You assume correctly. The needle jet is also called an emulsification tube.
 
Ok, the snow finally arrived as we got a nice 2' above 2600 feet and was FINALLY able to ride!! Everything ran great, but it still has a burble in the 4000 to 6000 rpm steady cruise range. Which is quite a bit of the time on the narrow, twisty trails we ride. It has no hesitation, miss or stumble when you give it the beans. I did do a plug read and certainly am on the rich side of things, which is where I wanted to be to ensure no burn down while tuning. The engine is very smooth, especially after balancing both clutches, and runs great except for the burble.

So my question is, is this normal? Can it be tuned out? My current setup is needle is at 3.5, pilot jet is 45, Pilot screw is at 2-2/8. Is the burble typically a lean condition, or rich?


I really appreciate any/all input.



Scott
 
I changed the needles back down to the 3 setting and it seemed to help. I did also install 47.5 pilots per the manual for my elevation (3300 to 5000) feet and temp (20-30) and it runs awesome! I got a nice comfortable plug read after a nice long steady cruise at 7000-8000 RPM, so I am happy with the high speed jetting.

However, it still has the annoying burble in the low rpm range. I paid very close attention to the throttle position and anything after clutch engagement to about 6500 rpm...say up to about 1/3 throttle (light load) it still burbles. In addition, it now has the infamous viper idle hang that it never really had before. My inclination is that the low speed 0 - 1/3 throttle is way rich, causing the tuned pipe to heat up. Can anyone give me some advice here? PLEASE!!!....lol

Scott
 
The idle should be set to 1500-1600 that helps with the hang. I noticed when I cruise steady mid range it would get a little burble, does it clear out after a wide open blast? Have you tried giving the choke/fuel enriching circuit a little lever and see if it gets better or worse?
 
Thanks Captn' I have for the idle hang, and it certainly drops it right down to 1600 rpm where it eventually goes. I have never tried it while riding while "in the burble zone" .. I will give that a try next time I ride and see what happens. These two strokes are a strange animal and all the things I know about doing this for 4 strokes just don't seem to apply...lol.

Scott
 
YammyScoot said:
Thanks Captn' I have for the idle hang, and it certainly drops it right down to 1600 rpm where it eventually goes. I have never tried it while riding while "in the burble zone" .. I will give that a try next time I ride and see what happens. These two strokes are a strange animal and all the things I know about doing this for 4 strokes just don't seem to apply...lol.

Scott
Click to expand...
Hey there, i know this is an old post but did you ever solve this burble issue with your viper?
 
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