I think I have a timing problem?

[Fletch]

Well i got similar problem on flat land if im running full throttle for over a minute it starts bogging down .And eventually dies and half to restart it. 1/4 mile is all i get at full throttle before it bogs down. And i dont see nothing on that carb to adjust beside the idle screw and that doesnt do much just idles it down or up what yah think is ours similiar or what?

I don't think so. On flat land or even slight grade I have no problem. It sounds like you have an air leak. Do you have an expansion chamber?


I have concluded by process of elimination that I am running out of fuel on decline/incline because the float is topping out sooner, so the bowl is not filling all the way. This is normal of course, but my expansion pipe must be revving higher and burning more fuel than the stock carb can replace with the small bowl.

Someone please correct me if you think I'm wrong. I don't have an air leak...I checked with butane everywhere and my carb is siliconed closed and to the manifold.

If I lengthen my header (lower revs)... will that fix it?

This can't be the result of having no base gasket right? I mean it can't thrown the timing off that much?

*** Update ***

OK so I want to fix this dying and revving a few times after on steep hills problem so I have a list of options here. Please let me know which ones I should try and in what order, or which would be more relevant...I think I have blow back into the intake possibly?

A) Get some copper pipe and lengthen the header some on my expansion chamber
B) Wait for a new carb upgrade (Speed or CNS)
C) Try using the jet from my broken Speed carb if I can figure out which one it is (ie. increase jet size)
D) Use a base gasket
E) Use a head gasket
F) Take the muffler off the pipe and see how it runs

 

[Dave C]

I'm thinking that without the gaskets when you pull a hill the temps go up and you have more expansion of parts and your seizeing up and when it's cooled down the clearances go back up and there's no problem. Look for scuffing or hammer marks on your parts when you put the gaskets back on

 

[Fletch]

Dave,

You're right!

I rode 80 miles on it 2 days ago up some monster hills! What I did was add a head gasket and gap my plug to .40. I know that seems huge, but Al fisherman recommended it in a thread and said it helped with hills. I did both at the same time, but I'm sure the head gasket made most of the difference.

On the 40 miles back home, by that time it had dropped from like 67 deg. to the mid 40's I'd guess, and there was zero vibration on the bike. Maybe I was just numb from freezing my *** off for so long, but I noticed a huge difference. This could also support your theory (which I now believe is correct). Doesn't the fuel lean out when it is cold, and that's why you need the choke to start in really cold weather?

I might even add one more head gasket to be sure there is no piston contact. I always assumed the piston would hit the plug 1st, but after looking closer I saw that the outer edge of the piston would hit the head before the plug would.

 

[Deleted member 12676]

Sounds like you solved your problem. I was thinking that if at full throttle it dies but not at half throttle then your main jet is too small.

 

[Fletch]

That's kind of what I was thinking. I switched over to the speed NT carb which supposedly has a bigger main jet, only I had taken the 3 nt's I've had apart and don't know for sure if I put the correct jet back in it. I had the same problem going up that hill again only I was able to pedal assist it without it dying. I ordered a Mikuni 18mm carb which will be here Mon. I'm going to see if that makes a difference. I ordered 2 jet sizes below what it comes with (90) and 3 pilot sizes to play with.