Yamaha Grizzly ATV Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
Hello all, just joined the site. Bought a Grizz a few weeks ago and cant get it to run right.

Has the Mikuni carb with all balls racing rebuild kit, done last october, new petcock, spark plug, battery, air and fuel filter.

Will only run with choke on all the way. My max speed is 41 and it takes forever to get there, zero throttle response.

Put a Caltric carb from ebay on the other day and tried tuning for hours and wouldnt work right. We Put the Mikuni back on.

Does this sound like a carb issue? Possibly a bad coil? Any help would be greatly appreciated.
 

·
Premium Member
Joined
·
9,834 Posts
Welcome from Colorado.
Add a signature so we know you ride, the signature shows in every post.
I suggest a full tune-up including the valve lash adjustment. The Yamaha valves are known to stretch and need adjusting after 1000 miles or less.
I've had several buddys with a 660 that got to running bad and a full tune-up got them going right.

edit...and have you tried it without the inline fuel filter? years ago I remember others saying these did not work well, I've never installed one to know for sure on my 660, never needed one.
 

·
Registered
Joined
·
2 Posts
Discussion Starter #3
Thank you for the input. I was told it was possibly the valves.

It had an oil change, carb rebuild, fuel filter, new battery, new petcock and air filter installed in October 2019 by Ebr performance of Houston Tx.

Bike sat in a garage until February.

When I got it, it wouldnt start, so we dumped the gas and it was a blackish brown color, and Mikuni carb had black gunk all over it. We cleaned carb and put new fuel filter on and its been doing the above described since.

Accelerates like a granny, top speed 41 running with choke wide open, sputters and backfires occasionally.

Starts right up first flick only with choke on.

Just curious, what is a "general" price for getting a valve lash adjustment? Thank you
 

·
Premium Member
Joined
·
551 Posts
Welcome, if your using the choke to run and start your bike all the time then your bike is starving for fuel, something is not right with your carb or you have a restriction, your choke adds fuel.
 

·
Registered
Joined
·
5,438 Posts
I am suspecting float height not adjusted correctly. The bowl is not filling high enough for the fuel to be lifted up through the main or pilot jets. When the rebuild kit was installed, it's a good chance they never checked or adjusted the float height. They just simply installed them.

The choke on these Yamaha's is not actually a choke. It's an enrichening valve. Simply put, it allows unmetered fuel into the engine.

I would first inspect and adjust the float height.

And most definitely check the valve clearances. Although I do not suspect this to be causing your specific issue at hand, they still need to be done.
 

·
Registered
Joined
·
204 Posts
"Will only run with choke on all the way. My max speed is 41 and it takes forever to get there, zero throttle response. "

Helped someone with a Bruin that had the same symptoms. I pulled the fuel line off of the tank/petcock, ran until carburetor was empty, filled fuel line/carburetor with WD-40, cranking some through, then another shot of WD-40 until the carburetor is full again, let soak for a while, crank it through again, check for fresh gas, hook up fuel line, crank until it starts, then test ride. It's been running good ever since for about 2 years now.
This Bruin was all original, never wrenched on, stored in barn, but rode hard and neglected.
The gas didn't look/smell bad either, but I topped it off with Shell premium gas.
 

·
Registered
Joined
·
339 Posts
Curiosity, what does the WD-40 do? It's made to dry out electric circuits, and remove water. Also has a bit of graphite in if I recall correctly, so they could call it a lubricant, but it's a poor one. Is it being used as a solvent?
 

·
Registered
Joined
·
204 Posts
WD-40 "Water Displacement formula #40". I would not use on things like Printed Circuit Boards due to the light oil which could attract dirt/dust. I use high purity contact cleaner "Freon" for that.

In this case the solvent helps to loosen and free the gummy carburetor deposits due to ethanol fuel. I've had success using it on carburetors before. It's a cheap and easy fix "when it works", before tearing into the carburetor. Probably won't work on a severely gummed up one though.

As for a lubricant it evaporates over time. I use it a lot to clean and protect the tools and machinery in the machine shop.
I'm under the impression it's a solvent with light oil, possibly a fuel oil such as kerosene. Never heard about graphite, it being gray you would probably see that.
BTW. They postponed the April 15th opening of the WNF ATV Monday Creek trails until further notice due to the china virus quarantine. They are open for hikers only.
 

·
Registered
Joined
·
204 Posts
Double post delete.
 

·
Registered
Joined
·
339 Posts
Yeah, it's purpose is to dry out electrical circuits, such as a fuse panel box, not necessarily printed circuits. It does not conduct, but bonds with water, then evaporates, taking the water with it. And it does leave a film behind that hinders water.
 

·
Registered
2017 Grizzly
Joined
·
334 Posts
will add a little as my prior 02 660 started getting hard to start and needed a lot of choke to keep running, a valve adjustment job solved the problem. I think the cost was @$200 at a local dealer.
While not sure if this might help; I also have a well used 22 year old log splitter that was requiring full choke to keep running, I took the muffler off and slowly introduced carb cleaner spray ( saw on a YouTube video ) began running smoother and was able to get running strong again and that was 3 years ago. It seemed to have cleaned out the jets/bowl for a cheap fix.
finding brown colored gas is not good so a full fuel system, carb cleaning and fuel filter would be in order.
 
1 - 12 of 12 Posts
Top