Intake Input/ Floundering Float

[bus driver]

I have a stock 91 EVO- EGC. My questions are, how loose should my intake manifold seals be? While reinstalling my CV carb, I noticed movement with the seals on the intake where they seat to the head. The intake moves fairly easily. There is some resistance, but I would think it should be fairly snug. My next question is, I seem to have a sticky float. My tank filter is clean, my inline filter is clean,and the fuel coming out of the fuel line is clean. I rebuilt the carb with a Made In The USA kit. But I still get a sticking float. Both open and closed position. When I rebuilt it, I soaked it in carb cleaning solution and blew out the carb with air. The rod that holds the float moves very freely and I am able to push it out with my finger. My float moves freely also. My tank is slightly rusty, but all of my fuel "appears" clean to the naked eye. I run Sea Foam and Marvel Mystery oil. I'm scratching my head and it's starting to hurt. P.S. 30,000 miles on the odometer. P.S.S. The float doesn't stick with the carb apart, go figure. Thanx Bus Driver.

 

[Jack Klarich]

Have you double checked the float height and you did use a new needle and seat?

 

[fin_676]

I am guessing by sticky float you mean that the float bowl overflow is dumping fuel to the ground
I would first of all suspect the float needle or the seat not being right the float needle has a thin rubber tip on it that fits in the seat and stops the flow of fuel a tiny bit of grit or dirt or wee bit of damage can allow fuel past the seal
Incorrect float height will also allow the float bowl to overflow
It is also not impossible that modern fuels have eaten a tiny hole in the float and that the float does not float too well

Brian

 

[bus driver]

When I rebuilt the carb it ran great for about 5000 miles. Then it started to feel like fuel starvation. When I was doing about 75 or 80, it would start to misfire I would slow to about 60 and it would regroup. I assume the float was stuck closed. So I rechecked the float height, which was still perfect. On occasion fuel would leak out of the overflow tube, but rarely. Finally the weather was decent here in the northeast the other day. When I went to start it, it wasn't getting fuel. So I dropped the bowl, and found the float stuck in the closed position. Freed it up and it's been fine. I did replace the needle and the seal on the tip of the needle that came with the rebuild kit. I'm thinking another rebuild is in order. I wonder if I the new type of fuel is causing my rubber to erode. The bowl was clean when I dropped it in the fall to check the float height adjustment. I don't have to worry about riding today because it's snowing like gangbusters here, and my bike handles like a 70 Caddy with bald tires in the snow. Thanx again, Bus Driver.

 

[fin_676]

Ethanol in the fuel will reduce the life of some plastic and rubber parts in the fuel system the rubberised tip on the float needle can go hard and fail to seal it could also stick
I have had to replace the float needles in all my bikes over the last couple of years and we only have 5% ethanol here in the UK
I think I currently get about 3 years out of a float needle and carry a spare float needle and seat in the bike tool kit my 2 big twins have mikuni hsr carbs and is a fairly quick and easy to replace needle and seat

Brian

 

[btsom]

I have never seen a carb kit that didn't have a needle and seat set. Any chance you tried to cheat a little and just use the new needle in the old seat (which might not be compatible with each other)? When you found the float stuck did you notice if it was a pivot problem, the float being off center so it was binding on part of the carb casting, or if the needle was stuck in the seat? While it is possible, I find it hard to believe that a modern carb kit would not be made up of parts tolerant to E10. If you still suspect the little sealing surface on the needle, it may be time for an E mail to the kit manufacturer to verify if their kits are compatible with modern fuel.

On the float/needle interface, is there some mechanism to pull the needle free if it sticks and the float drops toward the bottom of the bowl? Will that pull on the needle with just a small float drop or is the movement so big that the float will settle on the bottom of the bowl before the needle is pulled on?

If it were mine, I would find it easier to believe there is a mechanical binding of the float and carb body rather than the needle sticking in the seat and would check float freedom of movement when nudged full to one side of the pivot and then the other. Check for any wear marks on the float or on the carb body to suggest an interference point. I am curious if the float is brass or plastic. The overhaul kit should have a diagram of how the float should look when in the fuel stop position. Does your float closely match that diagram or is it tipped in some odd direction and needs to be reoriented. Without more information, I'm about out of ideas at this point.

 

[SledDog]

I'm thinking needle valve. The overflow issue point to that, if the float is correct. As for the misfire, it could have been some trash in the needle valve seat that caused the overflow. The misfire may not be related to the overflow issue.

Have you tested your manifold for leaks?

 

[bus driver]

I am going to have to drop the bowl again ( not now, it's 12 degrees out ) and see if there is any rubbing. The float is seated true, and I didn't notice any abnormal movement. When it was stuck in the closed position, it actually felt as if the rubber tip on the needle was adhered to the seat. Slight pressure and it was free. Then it was fine. It seems to stick open, and closed. Occasional over flow, and then what really feels like fuel starvation. Like when you have to go to reserve. I have a stock Keihin cv carb that I rebuilt with a James rebuild kit. The kit only came with the needle and not the seat. When the float is free there is no binding at all. I really think I'm going to have to do another rebuild. And to answer Sledgog suggestion, I really think I have to replace the intake seals. I feel there is too much movement when the carb is lifted. As in reinstalling it the carb. I really think there should be a little more resistance. I'm sure there should be a movement, but not as much as I have. Unless the bike is thoroughly warmed up,thoroughly, I will get popping through the carb. I do operate the enrichener as recommended, so that's what's making me think possible intake leak. Are there any easy ways to check for a leak? Like spraying starting fluid to check for a vacuum leak. I would hate to set the thing on fire. That would ruin my day. Thanx Bus Driver.

 

[fin_676]

To check for an intake leak you can spray wd40 or carb cleaner around the seals if the engine note changes there is a leak I personally use a gas torch that is not lit
The carb rebuild kit that you previously fitted may have been an old one that had sat on a shelf for many years and the tip rubber may be sticky or the needle is at a slight angle and jamming or there is a wee bit of damage that is causing the jam
It is time to get the tool kit out and start inspecting

Brian

 

[bus driver]

That's a great idea with the unlit torch. I'm going to give it a try. I just ordered another rebuild kit. It comes with new intake seals anyway. It's a good winter project. I still have the scars from the last rebuild when my Bride came home and found me reassembling it on the dinning room table. Maybe this time I'll try the bathroom. Thanx. Bus Driver