Blaster bogs, backfires when trying to maintain speed

[osphy]

Blaster bogs, backfires, idles low

I bought two blasters for $500. Decent little machines. I got them both running with fairly little effort. One runs great the other I am having issues with. The woodrift key was sheared and I replaced it.

I have cleaned out gas tank, changed my reeds, rebuilt the carb, checked for spark, and replaced spark plug. Drove down the road and it would not maintain speed. Bog down and sputter, run good, and again bog down. Constantly going in and out. Pulled plug and it was wet but I don’t think it was because it was running rich, I think it is just so boggy that it caused it not to burn fuel correctly. Runs decent when all out throttle but bogs and backfires when just trying to maintain a steady speed.

I was running stock with this issue but have put on new parts and still have issue. I now have put on new plug, KNN filter, vitos tors eliminator, full FMF pipe, switched to a 280 jet and still having the same issues stated above. It idles super low and cant tweak the carb to idle any better, when giving steady throttle in neutral or under load and it will sputter and backfire mid-range. All out throttle runs decent. Tweaked on carbs a lot and still is not any better.
I am getting frustrated but wondering what you guys think. I would do a chop test but afraid to run it with the backfiring occurring. I am going to do a leak down test as soon as I get a tester built but wondering what everyone thinks. I am leaning towards a spark issue, possibly a bad coil or wire. The stator sends a strong spark. Also do you think I need to adjust the timing or is stock timing usually okay.
APPRECIATE any and all help. Thanks!

 

[Quadman1]

Tors system?

 

[osphy]

Removed tors with vito kit and disconnected the three wire connector.

 

[dirtysquared]

Double check your reeds, and check to see if the woodruf key didn't break again.

 

[MrTwoJay]

Tors, reeds, timing (woodruff key)

That does not really sound like a fuel issue.

Remember, older model blasters the tors can simply be removed, newer models are not that simple as unplugging.

 

[MrTwoJay]

O, try using the CDI of the running bike, see if it makes any difference. ....

 

[bummer981]

How is your spark? do you have a strong blue spark?

The stator can be tested while in the quad with an ohm meter. You can also use one to test the coil. The values are in the manual.

 

[Blaaster]

When the woodruff key broke did you check the flywheel taper to see if it was damaged, if it was did you lap it. It may have sheared on assembly.

It to me shows symptoms of a slight timing issue which will tend to bog through the mid revs but clear up as the revs get to near peak.

A lean needle or an air leak will sometimes return the same symptoms.

Also a CDI which is sending the wrong signal can cause a problem.

Did you set the float level and is there a constant dribble of gas when you crack the float bowl drain?

Have you checked the filler cap vent for a blockage?

 

[osphy]

I would agree with you guys, I don't think it's fuel. Its a 99 so tors should be good. I'll try CDI box today at some point.

Just do a physical inspection of shaft or what should the call out be for the diameter of the shaft? I did not lap it and I'm not familiar with this process.
Float is good.
Have not checked filler vent and will do that.
What should my needle be set at?
It does have good spark. Do you guys have a link to a thread that would show me how to check stator and coil?
Thanks allot!

 

[osphy]

http://www.blasterforum.com/threads/i-have-made-the-blaster-repair-manual-searchable-enjoy.45582/

searchable manual. download it and search testing stator output

Thanks

 

[dirtysquared]

Here is the link to the manual. You'll Find the Ohm values in there for the stator. http://www.blasterforum.com/threads/downloadable-yamaha-blaster-manual.17325/

The needle clip should be on the 3rd slot(middle).

Lapping the flywheel to the crankshaft is a pretty easy. Get yourself some lapping compound, I think some sort of grinding compound will work. (I used an abrasive gun metal polish I have) Place the Flywheel on the crank without the woodruff key in the slot, then spin the flywheel on the crank. Stop when you get a good even finish. The flywheel is held on buy interferance from the taper, The woodruff key is just there to hold it in place so the timing is on when you install it. Re-install it, and tourque it to the proper specs. Those will be in the manual too.

Good Luck!

 

[osphy]

Here is the link to the manual. You'll Find the Ohm values in there for the stator. http://www.blasterforum.com/threads/downloadable-yamaha-blaster-manual.17325/

The needle clip should be on the 3rd slot(middle).

Lapping the flywheel to the crankshaft is a pretty easy. Get yourself some lapping compound, I think some sort of grinding compound will work. (I used an abrasive gun metal polish I have) Place the Flywheel on the crank without the woodruff key in the slot, then spin the flywheel on the crank. Stop when you get a good even finish. The flywheel is held on buy interferance from the taper, The woodruff key is just there to hold it in place so the timing is on when you install it. Re-install it, and tourque it to the proper specs. Those will be in the manual too.

Good Luck!

Thanks man!

 

[speedyslyder]

I had same problem when i bought blaster number 3 which is my current one ...It was the splash guard in the carb it was missing the part is called ring if you look it up under motosports oem yamaha carb ..i ordered the plash guard installed it and also remove the lid on air box since mine has toomey exhaust and i also installed 310 main jet ..person before me bought the toomey but did not follow through with jetting and crap .....make sure all the part are in the carb.....take lid off to see if that is problem....check you air screw .......the splash guard fixed mine plus took of lid ......peace not my carb but you get it

 

[Blaaster]

With all respect, a missing slosh guard should not cause the symptoms described by ospey.

The slosh guard is there to help control fuel turbulence within the jet area of the carb during hard cornering and rough terrain riding.

I feel that speedyslyders problem was rectified not by fitting a slosh guard, but by the fitting of a main jet which filled the needs of the Toomey pipe.

The stock Mikuni carb will run just fine without a slosh guard until you give the bike occasion to create turbulence within the fuel bowl.

 

[speedyslyder]

ok correction i re jetted mine took lid off and it still did it..while i was waiting for my part ...when i installed the part splash guard it fixed it...

 

[Blaaster]

With all respect, a missing slosh guard should not cause the symptoms described by ospey.

The slosh guard is there to help control fuel turbulence within the jet area of the carb during hard cornering and rough terrain riding.

I feel that speedyslyders problem was rectified not by fitting a slosh guard, but by the fitting of a main jet which filled the needs of the Toomey pipe.

The stock Mikuni carb will run just fine without a slosh guard until you give the bike occasion to create turbulence within the fuel bowl.

ok correction i re jetted mine took lid off and it still did it..while i was waiting for my part ...when i installed the part splash guard it fixed it...

I am not going to continue to argue with you on this matter, but I find it hard to swallow that the fitting of a slosh guard would fix bogging from being on the needle but running fine at WOT, as in the case of ospey.

Without the slosh baffle the engine should run fine until creation of turbulence due to very rough terrain or hard cornering which causes the fuel to climb the float bowl wall, away from the jet.

The slosh baffles primary job is to maintain fuel around the main jet to stop the drawing of air when conditions get rough, it does nothing to alter the jetting!