Author Topic: 90 won't run  (Read 4020 times)

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Offline guzzisvt

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90 won't run
« on: August 10, 2010, 12:49:40 PM »
I have a 1967 90 Sport with 8k miles. It's very clean and lookes well maintained. I'm getting a little frustrated. I'm a pretty good mechanic. One of my rules to live by is if you have fuel, compression and a spark it should run.
This 90 is testing my theory though. I bought it a couple of years ago and it always have a problem clogging up the idle jet. I would use the choke and throttle to get around this until I had time to clean the idle jet. Which was always dirt and would fix it until this time. Over the winter I replaced the leaky base gasket, put in new rings and cleaned the tank and carburetor. The bike started right up and I took it for a short ride around the neighborhood until I felt everything was alright with my work. Soon after that my wife and I rode it about a mile to breakfast. I notice the idle going away on the ride home but used the choke and throttle to get home. I took the carb apart to clean and found I'm still getting very fine particles in the gas so I installed a paper fuel filter to deal with that. After cleaning everything real well I still couldn't get it to run, only short sputters at mid or full throttle. I have spark but it does looks a little white. The battery seems to have some charge as the neutral light is bright, the guy I bought it from said it needed a good battery to run. I haven't checked point gap yet or timing but I always thought I was chasing a fuel problem until lately.

So what I'm I missing? The plug looks wet when I take it out, It even back fired through the carb once. It fires in short spurts but won't stay running. Fresh gas and ether didn't make any difference. With the pervious fuel problems it hard for me to move over to ignition or compression but I'm out of ideas.

Thanks for your input.
Bill
1967 90 S

bridgestonesforever

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Re: 90 won't run
« Reply #1 on: August 10, 2010, 03:14:11 PM »
I am no expert at all, but I am sure  the battery or its charge condition has nothing to do with spark, the bike
has a magneto ignition, so it will work without a battery. Luke

Offline BSOrion

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Re: 90 won't run
« Reply #2 on: August 10, 2010, 03:40:02 PM »
How does it respond to fuel sprayed directly into carb and/or hand over the carb to choke it?  If no joy, I'd suspect ignition and if you haven't already, I'd put a fresh (new), properly gapped plug in just for starters.  I've had plugs appear to be sparking fine but were bad.  It's frustrating when you know it's probably something simple!

There are some 50-pound brain motorheads on this site that will be more help than I... look for them to jump-in.

Orion
« Last Edit: August 10, 2010, 03:42:56 PM by BSOrion »

Offline guzzisvt

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Re: 90 won't run
« Reply #3 on: August 10, 2010, 04:01:24 PM »
Starter fluid did nothing, only seemed to piss it off. Seems to flood it more?
Best sputter was choke off, half to full throttle.
Bill
1967 90 S

Offline reed

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Re: 90 won't run
« Reply #4 on: August 10, 2010, 04:05:10 PM »
Guzzisvt
If you want to send me your carb and i will check it out for you go on to my web site carbworx.com
We will clear the carb and then we can go onto ignition compression check!
Thanks.
Reed.

Offline rocketman

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Re: 90 won't run
« Reply #5 on: August 11, 2010, 08:11:01 AM »
I just can't help but chime in on this subject. The old saying,"stick to the F.A.C.T.S.",comes to mind. Fuel,Air,Compression,Timing,and Spark. Not neccessarily in that order. If you are artificially supplying fuel to the combustion chamber,you should be getting at least a short burst even if the compression is low. Motor will want to run,but won't whithout a constant atomized fuel charge. If its wet and flooded already,then it sounds like theres plenty of fuel available. Of course the opposite is true as well,if its excessively flooded,it won't want to keep running until its cleaned out. Poor/weak or intermittent spark can allow the engine to load up. I would take a quick look at the points. Just run a point file or a double folded piece of emory cloth across them lightly right where they are. The object here is to clean any point burn, carbon deposits,or surface contamination off without removing too much meat. In other words,to brighten them up with out having to reset them. Visually roll the mag around to make sure they open and close,and give it a kick. If it helps,take a little time to reset or replace them and cruise on. If not,I'm confident your going to get more help here. Let us know.  Mark
« Last Edit: August 11, 2010, 05:37:09 PM by rocketman »

Dave K

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Re: 90 won't run
« Reply #6 on: August 11, 2010, 10:45:29 AM »
I agree Rocketman. Even if the crank seals were bad, it would still burn the fuel or ether off. I would, like you said, make sure the ignition system is clean and in time. See if there is excessive fuel from keeping it running. Actually turn off the fuel and only try to run it on any fuel that you are supplying through the carb. That way it may elliminate a flooding float or bad float seat. As I am sure all agree, if the 3 basic events are there, it will run. So, YOU provide the fuel to the engine, make sure that the spark is present and at the correct time and you can tell of there is compression.

Offline guzzisvt

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Re: 90 won't run
« Reply #7 on: August 11, 2010, 05:37:36 PM »
I picked up a new spark plug last night and plane to take a peek at the points and timing next.
I was a little suprised when it back fired though the carb but not run.
I check the choke, float and needle, they seem to be working fine.
« Last Edit: August 11, 2010, 05:39:48 PM by guzzisvt »
Bill
1967 90 S

Offline reed

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Re: 90 won't run
« Reply #8 on: August 11, 2010, 06:38:58 PM »
Guzzisvt
Trouble shooting
1 Do a compression test.
2 Pull carb clean all the jets pilot and main operation of float check float level rebuild carb clean
Is there clean fuel in the tank.
3 Pull off the flywheel and check the keyway if broken the timing is out.
4 Check points and gap 0.3mm-0.4mm.
5 Check you service manual to check coil and condenser.
Hope this helps.
Thanks.
Reed.

Offline guzzisvt

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Re: 90 won't run
« Reply #9 on: August 16, 2010, 09:47:24 AM »
Thanks for all the thoughtful advise. I put the new plug in it and it fired right up and ran perfect. I even took it on a 10 mile ride.
You know driving four strokes, even though my first three bikes were two strokes, you forget about those kind of things like fouled plugs.
I remember my brother had a three cylinder Saab two stroke. The glove boxes was always full of spark plugs.
I bought an extra one to keep in the tool kit!

Bill
Bill
1967 90 S

Offline rocketman

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Re: 90 won't run
« Reply #10 on: August 16, 2010, 01:00:56 PM »
Gussisvt, good news. Sometimes its the simple things in life that are so rewarding. Thanks for lettin' us know.  Mark.

Offline BSOrion

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Re: 90 won't run
« Reply #11 on: August 16, 2010, 01:03:26 PM »
Glad to here it was a simple fix... enjoy!

Orion

Offline reed

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Re: 90 won't run
« Reply #12 on: August 16, 2010, 07:12:13 PM »
Guzzisvt
Well done but i would still check the timing!
Thanks.
Reed.

 


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