XLV 540 Engine bog but starts and idles great

[mosabi]

Please help me. I was referred here from Sacha Hindle SRV540 proboards.

I have an '85 Yamaha XLV and I am stumped beyond belief.

History:
Newly rebuilt engine a couple seasons ago
New Boyesen reeds at same time
Newly rebuilt fuel pump (as of yesterday)
New fuel filter in tank
New plugs, tried multiple

The sled ran great last season and before this season I cleaned the carb like I normally do, heck I've cleaned it 3 times this season so far.

The sled starts and idles great but after giving it gas it just bogs and will not accelerate above 4k on a lift. New gas has been added and I add a bit of oil to the fuel like I normally do.

I am at a stand still and have no idea what next to try. Please help.

Hope this isn't against the rules but I have extensive info here on another forum. Please see: http://srv540.proboards.com/index.cgi?a ... 745&page=1

Thank you so much for any help you can provide.

[Vmax540]

Are the clutches clean and not binding from worn parts ?

[mosabi]

Could that happen just sitting a summer in my garage? I know nothing about clutches. Please advise what I would look for
Even better if there is a video I could watch.

Thanks for the reply!

[Vmax540]

Could that happen just sitting a summer in my garage?

Yes, especially, if any corrosion formed or dirt/grime had time to set up. First thing to do is take off the drive belt then get a can/bottle of engine degreaser/Purple power ect. and go to town cleaning the inside and outside of the Primary. Flush with lots of water then then dry completely using compressed air to blow the inside dry. Clean the both clutch belt surface's with a Scotch bright then use a clean damp rag and wipe clean. Hopefully your belt is within M.F.G. spec's. and also, clean and it would not hurt to clean it with warm water and soap.

[mosabi]

Thanks for the help vmax540!

I never got to the clutch tonight but here is what I did.

I re-adjusted the plunger so there is just a little play, no change.
I put a clamp on the pulse line going into the pump and also one on the line going to the fuel pump to ensure no air leak. I bought a new pulse line but never had enough time tonight to put it in. Man it looks like a chore to do that.... Although the pulse line was new a couple seasons ago...

Yep I was referring to the white plastic star, I raised the idle some just to 2k, I think factory is like 13-1500. The sled starts and idles AWESOME but after a warm up it has just enough power to move me at about 5-10 mph and if I gun it its like governed out and cant go any faster nor do the rpms increase. On the stand I can get it to 5k but there's nothing at full throttle let alone half.

I also replaced the belt with a different good one, the one I had was worn pretty good, this new different one sits higher in the secondary now.

I tried an Ignition coil pulled off an Exciter (same numbers) with the same results.

I am now leaning towards either carb now or clutches (which I don't know anything about).

Hell I could tear apart the carb in my sleep now if I had to.

My question about the carb is this: Are any of those 3 orifices on the air box side plugged by design?

I'll try to give a run down of what I do:
1. Take bolt out of float bowl, this releases the bowl.
2. In the bolt there is a jet (not sure of name) that I remove with a screwdriver
3. I then remove the float assembly and take out the needle and needle assembly with socket.
4. I then remove the center black plug (it looks ok). There are 3 holes (Left, bottom center, and right)
5. I then remove the jet ( again not sure of exact name) on the right side
5. I then then remove the jet in the center (large) hole. This looks like a long tube. No tiny holes in it on the sides.
6. I shoot every hole with carb cleaner and blow it out with compressed air in a can and put everything back in. For the jets i'll use a small piece of wire to ensure they are clean.

It just seems like one of the 3 orifices on the air box side is plugged by design.

Am I cleaning this thing right?

Oh I checked the exhaust too and it appears clear.
Boyeson reeds installed when engine rebuilt

Any more info would be greatly appreciated.

[mosabi]

Also what about my air screw being a potential problem. I am currently at 1 3/4 turns out. I notice the tip of the needle is ever so slightly bent. Do I not have the screw out far enough, is this maybe why I am getting a bog and not very good acceleration?

[Bob Vehring]

Well I would certianly give it a try, also on clutches check that the sec is ok, doesn't have a broken spring

[mosabi]

Thanks for all your help here and on the other site Bob!

Yeah I'll give the pilot screw a try and also in regards to the secondary. The spring seems fine, I can open and it closes

Where can I get carb parts like a seat assembly with needle and pilot screw if I need???

[Bob Vehring]

May be still from Yami, sites like SUDCO have a catalog you can download, not sure if they deal in Kehien
Maybe Chuck has a old carb he will sell, you never have enough spares

[mosabi]

Now this is a Mikuni on my XLV Bob. For the longest time I thought it was a Keihin but its a Mikuni.

I hear the Keihin would be a better swap. I don't know Chuck but maybe he will see this and chime in. Thanks for the referral.

More imortantly thank you for the much needed assistance!

[mosabi]

Tonight I cleaned the primary clutch, I did find one roller that was loose but since I don't have the part to replace it with currently I just put everything back together. I can now almost rule out the primary. Secondary opens fine and closes by itself. Could use a cleaning yet.

Never got around to starting it up tonight, too late to wake everyone up.

[Vmax540]

I'm a little confused...... are these a butterfly style like the Keihin on a stock Phazer or round slides ? B.T.W. I should have good used Y.P.Z. parts I could send for the cost of shipping.

[mosabi]

Hi Chuck!

The carb I have is a mikuni butterfly. Here is a diagram of it.

[Vmax540]

Is the T.O.R.S. Bypassed ?

I do not believe or see that the Mukuni's have the rubber plugs like the Kiehin butterfly carbs ? One rubber plug on top of the pilot jet the other beside in the center hole. I do know the Kiehin will Not rev if the pilot jet is not covered !

[mosabi]

#13 on the diagram is the plug. I have it in the center hole of the 3 surrounding the main.

TORS has been bi-passed since I've gotten the sled.