1988 Suzuki LT 4WD - Starting Issue

[mikejh 10]

Hi,

I have an old '88 LT-4WD, and it has been sitting for about 3 years. A few months ago, I re-built it, including cleaning the carb, changing all the oils, re-did alot of the electrical, bled the brakes and cleaned out the master cylinder, replaced the rings, valve seals, oil seal, and gaskets. (among many other things) It ran fine for awhile, but now it has trouble starting. For awhile it started with full throttle and the enricher down, but not even that works now. I have spend many hours trying to start it, and havent had any luck. I replaced the spark plug, (it had good spark, but may not have under compresion) I also took the carb apart again to see if somthing plugged the jets already, but they were fine. I am just baffled. Any idea's would be appreciated.

Thanks!

Mike

[pmnova 10]

What did the the spark plug look like ?

[mikejh 10]

When I re-built it, I put a new plug in, and it looked fine. Definately not fouled. I put the old plug back in to see if that was the problem, but it didn't make a difference.

[pmnova 10]

Try pulling the plug and spray some wd-40 into the cylinder, reinstall the plug and see if that makes a difference. I would recommend doing a compression test before and after doing the wd-40 trick to see if good compression

[mikejh 10]

Will do. Thanks.

[mikejh 10]

I just went and put dw-40 in the cylinder and still no change. Unfortionately I don't have an adapter for my compression tester that works with this small size plug, so I don't know what happened with the compression. It has always felt good, but I have never put a tester on it to make sure.

[oxidized_black 78]

are you getting fuel to the carb? are you getting spark? is your timing off?

what cc is your bike? maybe i have the manual which might help you out ...

[mikejh 10]

Yes, I am getting fuel. I have good spark, and as I said above, I have tried 2 plugs. I just re-built the cylinder, and am pozitive the timing is correct. It ran for about a month after re-building it and the timing was fine, so unless it slipped, I don't think that is the problem.

It is the 250. I have a service manual for it, but the trouble shooting doesn't go very far beyond checking for spark and fuel.

[pmnova 10]

You sould check the engine for proper compression. If the compression is low it cant create the vacume to draw fuel into the cylinder

[pmnova 10]

Also how are u checking spark? Just because u have a spark doesnt mean u have a spark that hot enough to ignite the air fuel mixture

[mikejh 10]

I will get an adapter for my compression tester asap.

To test the spark, I leave the plug in the boot, put it close to the frame, and turn it over. The spark idn't that strong, but it is enough to arc to the frame. (about 1/8")

[JustRandy 51]

I've seen these engines run with almost no compression. I wouldn't sweat the compression test. The stroke is so long that you would have to have a gaping hole the size of your finger for it not to develop enough compression at starting speed.

3yrs is a long time. Did you clean the crud off the inside of the fuel pump? How about the petcock? That could be dumping gas into the vacuum line if the diaphragm is torn. That's a VERY common problem on these quads. How did you clean the pilot jet? I had to use very small drill bits on mine (like #90 and higher). I thought I had the 37.5 pilot clean until I saw the 35 pilot I had was bigger. So I had to drill it out again. Its amazing just how hard and tough that crud is that gas leaves behind. Its almost as hard as the brass! Guitar strings or bread ties make good jet cleaners. Also clean the little holes in the carb itself. Not just the jets. Those holes are hard to get to. A guitar string works good for that.

For hard-starting issues I always verify the intake valve has enough lash. Its pretty well known how hard it is to start a cold engine if the intake valve has no clearance. Since you just rebuilt it and it ran for a while, I would check that 1st. If the valve is tight, then you have dirty air passing thru your filter. Now that the hardness is worn off the valve, this will happen more frequently until the valve is finally worn away and pulls thru the head. I've seen this a lot on these heads and its pretty much a given when one rolls in my shop.

[oxidized_black 78]

I will get an adapter for my compression tester asap.

To test the spark, I leave the plug in the boot, put it close to the frame, and turn it over. The spark isn't that strong, but it is enough to arc to the frame. (about 1/8")

gotta be bright blue and rapid fire consistant ... yellow is weak ....

[mikejh 10]

I've seen these engines run with almost no compression. I wouldn't sweat the compression test. The stroke is so long that you would have to have a gaping hole the size of your finger for it not to develop enough compression at starting speed.

3yrs is a long time. Did you clean the crud off the inside of the fuel pump? How about the petcock? That could be dumping gas into the vacuum line if the diaphragm is torn. That's a VERY common problem on these quads. How did you clean the pilot jet? I had to use very small drill bits on mine (like #90 and higher). I thought I had the 37.5 pilot clean until I saw the 35 pilot I had was bigger. So I had to drill it out again. Its amazing just how hard and tough that crud is that gas leaves behind. Its almost as hard as the brass! Guitar strings or bread ties make good jet cleaners. Also clean the little holes in the carb itself. Not just the jets. Those holes are hard to get to. A guitar string works good for that.

For hard-starting issues I always verify the intake valve has enough lash. Its pretty well known how hard it is to start a cold engine if the intake valve has no clearance. Since you just rebuilt it and it ran for a while, I would check that 1st. If the valve is tight, then you have dirty air passing thru your filter. Now that the hardness is worn off the valve, this will happen more frequently until the valve is finally worn away and pulls thru the head. I've seen this a lot on these heads and its pretty much a given when one rolls in my shop.

Yes, I cleaned the fuel pump. Haven't done anything with the petcock though. I know for sure that the carb/jets are cleaned out well.

I will check the intake valve. Its a pain to have to take the head off again...

Oxidized, the spark is bright blue, and for this small engine, should be strong enough.

Thanks for the tips guys.

[oxidized_black 78]

there should be an inspection cover to avoid pulling the head. you can measure your clearences there too. good to hear you have good spark too !!

[mikejh 10]

Do you mean the black rubber plug on the side of the cylinder?

[oxidized_black 78]

not sure with suzuki, yamaha has inspection covers front and rear, intake and exhaust respectively ...

3 bolts each on mine ...

[JustRandy 51]

There are caps on the valve cover with big nuts on them. Like a 21 or 22mm socket. I can't quite understand how one can be savy enough to assemble the engine, but not know about the valve adjustment access holes.

The big round holes:

If you put the head on I hope you didn't use too much RTV on the valve cover or it will squeeze into the cam bearing quite easily. It will burn up the cam bearing and make the head junk.

[mikejh 10]

There are caps on the valve cover with big nuts on them. Like a 21 or 22mm socket. I can't quite understand how one can be savy enough to assemble the engine, but not know about the valve adjustment access holes.

The big round holes:

If you put the head on I hope you didn't use too much RTV on the valve cover or it will squeeze into the cam bearing quite easily. It will burn up the cam bearing and make the head junk.

Thanks for pointing them out. Pretty funny I didn't know! This is the first small engine like this I have rebuilt, so bear with me. I have worked mostly on cars.

I used very little RTV for that reason, and would be very supprized if any squeezed out.

[Ctwolframs 10]

I have been working on a 1987 lt4wd for the past year or so. My experience, the carb may be the issue. I rebuilt mine 4 times (moose parts), soaked, sprayed, everything. Finally broke down and bought a carb on eBay. Installed, started right up. Idle was uncontrollable. Replaced the throttle cable, runs perfectly now. Besides a slipping clutch! If you rebuilt the carb go back to the original parts, and check the cable for play. Good luck. Dan