Feedback on my build YZ 125 Shifter. PICS

[cody89]

I just completed the YZ 125 shifter kart build. However I am having issues with fuel getting to the carb. I have did some tests and it seems that the pulse is not strong enough. I read online that the pulse line needs to be less than 12" and right now it is probably around 16". I can suck/blow in the pulse line and I can see fuel come out of the fuel line going to the carb, but when I hook it up to the barb fitting I installed in the reedcage no fuel comes. I am going to make it closer to the fitting but was wondering if it was OK to mount it to the engine. I was thinking about mounting it off the coil which is mounted to the head. Here are some pictures showing the current setup.

http://i.imgur.com/RXcGY2Bh.jpg

http://i.imgur.com/7rF0Hlzh.jpg

http://i.imgur.com/m2KyzOdh.jpg

http://i.imgur.com/ac8qg4xh.jpg

 

[OzFab]

The head will become the hottest part of the engine &, given that heat rises, it may not be a good idea to mount a fuel pump anywhere near it. Why not mount it on a bracket attached to the rear engine mount?

Once you do get your fuel delivery problem sorted, you may have another problem with the carb sitting on a compound angle; not only is it tilted forward, it's tilted sideways too!

 

[cody89]

Thanks for you input. I will look into mounting it right there. But I am open to other suggestions.

As far as the carb, Does it have to be at a straight upright position? I have never dealt with 2 strokes or engines this size so I am not sure. The parts are all stock so that is the normal position it sits.

 

[anderkart]

I think the easiest thing to try first would be replacing your pulse line with some 1/4" fuel line made for cars. That racekart fuel line expands/contracts a bit weakening the signal arriving to the pump, It' works fine for a shorter length, but your pulse line is pretty long... Also, get some small zip ties to install as hose-clamps on ALL your pulse and fuel line connections. (your pulse and fuel tank connections might be leaking/sucking air)

If that doesn't fix your problem, it's actually pretty common for shifterkarts to install pulse pump mounting bracket to the cylinder head bolts. Sharkshifters sells a mounting bracket like this for CR125's, probably wouldn't fit your YZ, but you could build one. Although I think mounting the pumps bracket to your engines sidecover bolts might end up keeping the fuel and pump a bit cooler.

 

[cody89]

Is this what you are talking about?

 

[cody89]

I did some modifications to the setup. I shortened the pulse line to about 8 inches and I have used some 8mm auto fuel line. It is hose clamped on both ends so it isn't leaking. I also moved the fuel line on the pump from the one directly across from the "IN" to the one on the side. I can now see fuel SLOWLY move. It still doesn't look like it works like it should though. Attached you can see in the yellow fuel line that there is a spot where the fuel is. I did about 100 kicks and the fuel never moved up to the carb from the spot it is at.

Any more suggestions?


http://i.imgur.com/JjglGrF.jpg

http://i.imgur.com/wAOEVGa.jpg

http://i.imgur.com/oMTtokq.jpg

 

[OzFab]

Dude, you need to reduce your pics, they're really hard to look at...

 

[anderkart]

Sounds like your needle and seat valve might be dirty/stuck closed in your carb.
Or maybe your carbs float bowl is already full, and the needle and seat valve is working fine and simply wont allow any more fuel into the carb.

Does It pump better when you remove the line to the carb?

Remove the drain plug from the bottom of your carb. (does any fuel run out?)

With that drain plug in the carb removed, see if you can blow air into the carbs fuel inlet. (If not, your needle and seat valve is stuck closed, or a fuel passage is dirty/plugged up inside the carb)

PS:
Keep in mind its normal to see air-bubbles in the line going to the carb.

 

[cody89]

Just an update.. Blowing into the pulse line does nothing. I have to suck blow suck blow suck blow etc to activate the vacuum.

When I do that the pump works like it should but it doesnt push it all the way into the carb. It will push the fuel up until the fuel line starts to arch then it stops. It only wants to push it up, not down or sideways.

Also, I took the carb bowl apart and it had a bunch of crystalized fuel. It was smushy like jello. Most likely from previous owner.

After I did that I filled up the carb bowl with some fuel. Should I have did this?

Also, it seems like every time I pull the plug, it is wet with brownish fuel. So I wipe it off, put it back in kick it a few times, get maybe one small fire, then pull plug and it looks the same.

However after the carb cleaning it has fired more often, but still not starting.

As far as spark, I am getting spark. It is a small blue spark. Not sure if it should be bigger or not.

 

[landuse]

Just an update.. Blowing into the pulse line does nothing. I have to suck blow suck blow suck blow etc to activate the vacuum.

When I do that the pump works like it should but it doesnt push it all the way into the carb. It will push the fuel up until the fuel line starts to arch then it stops. It only wants to push it up, not down or sideways.

Also, I took the carb bowl apart and it had a bunch of crystalized fuel. It was smushy like jello. Most likely from previous owner.

After I did that I filled up the carb bowl with some fuel. Should I have did this?

Also, it seems like every time I pull the plug, it is wet with brownish fuel. So I wipe it off, put it back in kick it a few times, get maybe one small fire, then pull plug and it looks the same.

However after the carb cleaning it has fired more often, but still not starting.

As far as spark, I am getting spark. It is a small blue spark. Not sure if it should be bigger or not.

You are going to have to clean the carb out totally. It sounds like you just took the bowl off. You are going to have to take all the jets out, poke out any holes in the jets, etc. Taking the carb off completely makes things a lot easier

 

[cody89]

I am not sure where the needles are on the carb but what I did was take the bowl off. Clean out the bowl. Then I cleaned the two floats, the peice that moves based on where the floats are, the little needle under that, then I unscrewed a brass fitting and cleaned it. I then cleaned all holes in the float area.

Then I took the top of the carb off where the throttle cable goes and sprayed the slide and the longer needle off. Then sprayed the whole carb down in and out about 5 times.

I did some posting on another forum more about shifter karts and it turns out the pulse line fitting should be BEHIND the reedcage. So the video above that shows putting the fitting in the tubing is wrong. It needs to be..

Air Filter > Carb > Reed Cage > Fitting > Internals

NOT

Air Filter > Carb> Fitting > Reed Cage > Internals

I am going to plug the hole today and redrill a new one. This will give me the pulse I need.