4 hp Lightwin won't stay running

[Don Hansen]

I have a 1970 4hp Lightwin that started to act up while on a fishing trip. Here are the symtoms. Most of the time when pulling the rope it hardly tries to run. Sometimes it will run for just a few seconds, sometimes 10 to 20 seconds or longer. Three or four times it ran fine for more than 10 minutes. Then it starts to slow down, still running smooth, just like the throttle is being turned back until it stops. Keeping pressure on the primer bulb does not help. Taking out the high speed adjustment screw shows the carb is getting plenty of gas. The plugs show signs of gas but it's not flooded. It's pumping plenty of water, although I did find out on this site that there still may be a blockage. Someone pointed out that it seems to make a squeaking sound as it's slowing down but no binding is felt, or squeak heard, when pulling the rope. It has lots of spark, flywheel has been off twice and no problem found except the plate that holds the points has a bit of side to side play. Not sure if that's normal. The carb has been taken apart three times, cleaned it with carb cleaner, and no problem found. After returning from the trip, and the motor having sat for a week, I took a compression check with the motor cold. I got 90 lbs upper and 80 lbs lower. After squirting in some fogging oil I got 130 and 125 lbs. With the carb off, holding my thumb over the intake I seem to feel nothing. Not sure if that's normal.

Don Hansen

 

[Xcusme]

Re: 4 hp Lightwin won't stay running

Don, Welcome to iboats!

There are some things to check, beyond what you've already looked at. Are the coils cracked? You could have one or both coils going bad when they heat up, killing spark to either or both cylinders. Have to cleaned and re-gapped the point sets? Clean and adjust the points to .020. Align the crankshaft key with the points rub block when you adjust the point gap. When running and she starts to die, use a spray bottle filled with fuel mix, and spray a bit into the carb throat as needed to keep her running. If you can keep her running with the spray bottle, it points to a fuel delivery problem in the carb.
If there's a too much up and down play in the armature plate, there's a fix for that too. The fix involves removing the armature plate.


Here's a post from our good friend J. Reeves that explains the 'fix' for a wobbly armature plate. His reply helps a fella with a fix for a motor that fires on only one cylinder, but the fix applies to your situation too...

"That problem is usually caused by one of two things (or both) assuming that the points, condenser, and coil are okay.The first is that one of the spark plug wires has chaffed through which allows it to ground out as the armature plate turns.The second is that too much rocking type motion exists in the seating of the armature plate (the plate the coils etc are attached to). The solution to this problem follows.

(Magneto Armature Plate)

If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically as the armature plate turns. The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make an indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort."

 

[Don Hansen]

Re: 4 hp Lightwin won't stay running

Sorry I didn't respond sooner. My DSL has been up and down the last couple of days. Will try your suggestions but first, to run it, I will have build a frame to run the motor in a garbage can as it's a long shaft. I'm not a novice at working on engines but there's nothing like having a service manual so I think I'm going to be ordering one.

I do have one question. The motor being a 2 stroke I don't like the idea of putting something in the gas, or spraying something into the carb while it's running, to clean the fuel system. Is there something that is safe to use.

Don Hansen

 

[Xcusme]

Re: 4 hp Lightwin won't stay running

I do have one question. The motor being a 2 stroke I don't like the idea of putting something in the gas, or spraying something into the carb while it's running, to clean the fuel system. Is there something that is safe to use.

Don Hansen

Spraying 'cleaner' into the carb throat doesn't do anything to clean the carb internals. It can do harm to the motor as well, the carb cleaner sprayed into the throat will strip any lubrication from the cylinder walls, and that's not good. Carbs have to come apart for proper cleaning. You can use Seafoam in the fuel mix to maintain the fuel for storage etc.

 

[Don Hansen]

Re: 4 hp Lightwin won't stay running

Finally ordered and received a carb repair kit and manual for my 4hp. I wanted to make sure I got quality parts so I ordered an OEM kit. I was surprised to fine that the float needle was all medal and had no rubber tip. Isn't a rubber tip better? The one that's in the carb now has a rubber tip.
I have another question. Is it safe to remove the high speed nozzle when cleaning the carb. Looks to me like it is turned in to a certain depth at the factory because of the amount of thread left over.

Don Hansen

 

[tashasdaddy]

Re: 4 hp Lightwin won't stay running

remove the high speed jet, it screws in to bottom out. carb tool

 

[Don Hansen]

Re: 4 hp Lightwin won't stay running

Thanks
Here's another question. The kit came with a welch plug to replace one on the carb. If the one on the carb is in good shape is it necessary to replace it. What I mean is, will soaking the carb in cleaner and blowing it out with compressed air do a good enough job of cleaning the passage under the welch plug. I'm worried about damaging the carb trying to get the old one out.

BTW
I felt the fix for a loose armature plate as described was too temporary so I made a washer out of 0.005 brass shim stock. Turned out real nice.

Don Hansen

 

[HighTrim]

Re: 4 hp Lightwin won't stay running

No, you must remove the plug and clean beneath it, just puncture it slightly with a center punch or the like and pop it off. This video may help for your first time. Good luck.

"http://www.meegsonline.com/tmd/TMDsVideoChronicle2.wmv"

 

[Don Hansen]

Re: 4 hp Lightwin won't stay running

Thanks, the video was helpful in other ways too. Those who view the video should pay attention to his warning about carb cleaner in an inclosed area. 25 years, or so, ago I overhauled a Quadrajet in my basement in the middle of winter. I was using Gumout brand carb cleaner to soak the parts in. By the time I was ready to put the carb back together I could not read the instructions. I lost a weeks work because I could not walk more than a few feet before my legs would hurt so bad I had to lay down.


Don Hansen

 

[samo_ott]

Re: 4 hp Lightwin won't stay running

Just reading this thread now. I didn't think there was a high speed adjustable jet in a 1970 model. Is it the low speed you are adjusting? And interesting about the rubber yipped carb valve as I thought they were all metal... maybe they changed later on...

Spraying premix (oils and gas) in the engine while running is ok, just dont spray anything in that does not have lube in it. Seafoam says it does have lube so that it is ok to spray in.

 

[Don Hansen]

Re: 4 hp Lightwin won't stay running

Yes, it has both high and low speed adjustment screws. I bought the motor used in the mid 70s and had always thought it was a 74 model until I looked it up. It's a 4006, which makes it a 70.
Here's a question. I've built a stand so I can run the motor in a garbage can once I get the carb back together. In my area, Milwaukee WI, we have the gas with 10% alcohol. I could get gas without alcohol but it's a 40 mile trip, one way, to get it. What problems can be caused by using gas with 10 % alcohol in it.

Don Hansen

 

[Don Hansen]

Re: 4 hp Lightwin won't stay running

Got the carb for my 4hp back together today, set the points using a feeler gage and used the ohm meter method to verify. The motor started on the second pull and except for the times I turned the motor off to check how hot the block was, it was just good and warm, and move an inline spark tester from one plug to the other, it ran great for about 3 hours. After that I winterized it.
Never did find anything that I could say "That's the problem".

Thanks for all the help

Don Hansen