opsmgr

Ok, now the track bike is playing up. I knew laying it up in a damp shed for 3 years was probably a mistake

I has fresh fuel in it, and i've put some redex (carb cleaner you put in the fuel) through it.

The bike refuses to pull over 5k rpm, but starts and runs fine below this. It could be some sort of fuel starvation, problems with the tap, dirty or gummed carbs or perished diaphragms etc.

I don't think any hoses are pinched, as when I parked the bike, it was running perfectly, and nothing's been changed since. (yes, yes, I should have drained the float bowls )

Any ideas where to start ? I don't fancy tearing it down much, but looks like i'm going to have to start investigating somewhere ...

Has anyone seen these symptoms ?

Thanks,

Paul.

PUSHrod

Look for cracked, loose or disconnected vacuum lines from the petcock to the manifold. No vacuum means no fuel flow at high demand. Also in the category of free or cheap, are the air ways clear, you know, the snorkle under the triple tree, the air box/filter set up etc. Mice and other critters have been known to build nests that block air passage.

If it starts and idles okay, then the low speed jets are clear, they would clog before the high speed jets and the emulsifier tube, so the big jets are probably okay.

Northern Ireland, damp shed, three years. Yer gonna be lucky to get off easy and cheap.

opsmgr

Prize of your choice to the man over there. I did check the petcock pipe, but (very) close inspection reveals some tiny pinholes right up by the tap that I can suck air through.

I'll chop it down and test it, but looks like i'll be replacing the vac pipes. Don't want that failing and leaving me stranded !!

Edit: Didn't solve it. Seems the pinholes aren't bad enough to starve fuel. Now have tank, airbox, carbs off :-(

Ha ! thanks for that. Well, this bike has just gone back on the road after a long, long absence. Passed the MOT today !!

Cheers,

Paul.

Circuit_Burner

Storing a bike for over a year without draining the carb bowls 1st guarantees the need for a carb teardown and dip in most cases.
The fuel remaining in the bowls turns into something similar to thick coffee syrup and clogs pilot jets and many other things like CV slide operation.
I resist putting any pooky in the gas as a solution, unless you are desperate to avoid the formal teardown and cleaning operation.
Anything stronger than seafoam causes issues other than what you had originally.

RK1

I'll tell you this based on personal experience;

When you leave a bike with gasoline in the tank for a few years, the least of your problems is gonna be the carbs.

Drain the bowls, close the valves, disconnect the fuel lines, pour in some Yamaha Carb Cleaner. Rock the bike every 15 minutes for a few hours and the carbs will be as good as new.

Rust in the bottom of the fuel tank is going to be a way bigger pain in the *** to fix.

Hawkrider

I'm surprised it idles at all! Sounds like you may be in luck. One big thing you'll want to be looking out for is sticking float valves though. If it sticks open you'll be suckin, literally - suckin fuel out of your cylinders after they fill up. If you want to try to clean these up without pulling the carbs try this:

Manually exercise the slides a bit and put some silicone spray on them. Next drain the bowls by opening the drain screws. Try to collect the gas, or whatever comes out. Inspect it for water or other junk. Use 1/2 bottle of seafoam and ride the hell out of it for at least a tankful.

Good luck!

opsmgr

Thanks for your input guys. Can you get the float bowls off with the carbs in situ ? as the carb assembly is a pain in the *** to get off the front head.

I've left the fresh fuel & cleaner in it overnight, to see if anything loosens out.

I can say for definite that it's not the diaphragms, as the slides move ok when the engine is running, it just doesn't seem to be delivering fuel over 4k RPM.

I'll go at it again tomorrow. I'm 90% sure it's the carbs, not the tank or the fuel ****.

Cheers,

Paul.

Hawkrider

Exactly! What do you think delivers fuel over 4k rpm? The needles, which are controlled by the slide position. Gunk between the needle and the main may be causing stickiness.

fuzzuki

I'll be willing to bet he's got mice in the air box.

Circuit_Burner

mice, lol.
We had a VFR 700 87 model come in our shop back in 89, and when we took the airbox cover off, dogfood spilled out everywhere, LOL
Mice had stashed stolen dogfood inside the airbox on top of the air cleaner element.

opsmgr

Thanks again all for the input. Someone else has suggested that it could be electrical/ignition, especially when it idles ok, so the fuelling may be a red herring.

Looks like i'm gonna be b@lls deep in the VTR again today instead of riding it

However, it's great to have a working one next to the poorly one, it's a great source of testing spares !

Paul.

Thumper

K.I.S.S.

If it was running fine when you stored it then it isn't electircal unless bad battery.

You are going to have to pull those carbs and clean them out.

opsmgr

You're right. I was just postponing the inevitable.

I pulled the carbs, fuel in the float bowls (good start !), no rust in the bottom of them (even better) and the float needles seemed clear.

I'm thinking that the huge lump of crud in the main jet wasn't helping, I couldn't even see light through it

Changed the jets, as I had a couple of spares. Just road tested it, sorted.

Cheers,

Paul.

Hawkrider