XLV 540 Engine bog but starts and idles great

[Super Stock]

the pipe is plugged up try it with the pipe off

[keno]

Chuck, you say you're a little confused. I think you are too.

You should take a look at some Phazer carbs. They say MIKUNI on them.

Mosabi has a Mikuni like he says. That is what came on XLV's (and VK 540's) and look just like his picture from Yamaha microfiche.

Keihins were on SRV's, SS440's, 440 exciters to give a few examples.

The Mikunis have the plugs he's talking about. Keihins don't have them.

[mosabi]

I do have a different used exhaust pipe I can throw on there in testing or I'll try it without. I'm gonna ground the engine first before I try it.

The sled sat in my garage attached to my house all summer long covered up. I highly doubt a critter got up in there and built a nest of some sorts but who knows. It worked fine last year.

[opsled]

You can check the pipe by running the sled on a stand with it off. If that improves how it runs you may have your problem. They should run better with the pipe on.

I would not eliminate those reeds from being the culprit either. They have been said to have issues with ethanol fuels that result in symptoms that are very much like yours.


opsled

[Vmax540]

I am a little less confused due to Keno setting me straight..... But, I do know if you do not cover the pilot jet with a rubber plug on a Phazer it will not rev and you'll be lucky to get up to 10 M.PH. ?

[keno]

Hi Chuck

Glad I could help you remember which was which. I'm always confused when messing with these butterfly Mikuni's.

I have an XLV carburetor that only has one plug in the center hole, nothing over the pilot jet. You can't put a plug over the pilot because the hole is very slightly smaller. It was built that way and runs just fine. I have no idea why this has one plug and the the Phazers have 2 plugs. The VK 540 with a single butterfly Mikuni has 2 plugs just to add to the confusion.

The pilot jet is a #60 in the XLV and a #90 in the VK so maybe it has to do with pilot jet size. The Phazers have #95 pilots. It seems like the bigger pilot jets have a plug over them and the smaller ones don't. But why it was done this way is a mystery to me. (other than to keep us all a little confused)

Do have to agree about a Phazer running like crap with the plugs not in the right spots. You can probably guess why I know that.

This isn't a lot of help to Mosabi but it sure seems like he has a carburetor issue

Ken O

[Vmax540]

I had a sled that would not rev and after pulling my hair out, finally, changed the CDI and whoa-la..... never looked back !

[mosabi]

Update!

Well I think I am onto something here. I grounded the engine to the chassis, turned out the air screw on the carb one more full turn so its 2 1/4. I was running it at 1 1/4 last year so that's where I left it. Added another gallon of fuel and gapped my plugs to .031. It started up on the third pull (it was sitting for at least a week or so where I never touched it).

I warmed the engine up for about 5 min, idled great like it always did. After that I lifted up the track and gave it the goose praying for the best expecting the worst and she took off like a raped ape. I took it down the street without the seat on and it had all the power in the world, this is how I remembered it last year. Drove it about a half mile and it ran great.

Do we suspect a ground issue here? I did gap the plugs and adjust the carb again.

Now we have -40 with wind chill and its not suppose to warm up until next Friday.

I'm pretty excited to have it running like it should again.

[Bob Vehring]

Mo, finally great news keep at it for a few days to make sure it stays good, then I would look over the wiring real good to see where you lost the ground, make sure all lights and acc's work

[Super Stock]

I think the key was added gas check pick up in tank.

[Vmax540]

Good news, I have heard of grounds causing dim lights or hand warmers that do not get hot.

[mosabi]

I haven't ridden it since I got it working but I got the seat and everything back on and it's ready. We just need more snow as we lost some this past weekend. Pickup line in fuel tank was fine but my question is this. The fuel filter sits vertical in the tank and it has the white tube around it keeping it from moving. The filter attached is about 2 inches long and has an aluminum mesh around it. My question about the filter is and maybe I won't make sense here but is the opening on the bottom of the filter inside of it or how large of opening does it have inside? I'm used to the small filters with the weight in the end but this is a huge filter. Wondering if the gas gets to low it won't get proper pickup without air.

Hope this made sense.