Could it be...hmmmm.....Satan? or possibly my coil?

[JD_Sledder68]

Ok....had the 78 LF 340 out today with the wife on it. It seems to run about 20 to 30 minutes and then starts losing power and then dies. I removed the tank and drained/flushed, replaced the line, filter/pickup in the tank and topped off with fresh fuel/oil mix this week. I went through the carbs a couple of months ago....cleaning jets/pilots/bowls and new gaskets, set idle mixture screw and idle.

This thing runs like a scalded dog in that first 20 to 30 minutes. Doesn't matter if you run it hard or just putz around on it. Wife doesn't run it hard. Probably only runs at about 20mph most of the time.

If you let it set for few minutes it will start back up and then die. If you let it set for an hour or so and get good and cold it will start and run just fine and we start the cycle all over again.

I thought originally, that it was the broken fuel pickup line and debris in the fuel tank, but now I don't believe it is a fuel distribution issue as the fuel lines from the tank to the carb inlets still show full of fuel.

I haven't checked the crank seals, but the spark plugs are medium tan and the impulse line gets really good vacuum when idling. Although it is possible that the seals are good when cold and go south when warmed up. Engine will get torn down and gone through over the summer just for sh|t$ and giggles.

Does this sound like an ignition coil issue or maybe CDI or do I have issues??

[lwb140]

im guessing cdi or ststor just me wade

[JD_Sledder68]

Oops....I meant stator or cdi. I have a spare CDI, I think I'll swap that first and see if it makes a difference. Weren't the CCW engines notorious for stator and CDI problems?

[400brian]

Yes, the Prestolites were prone to failure.

When it comes to race sleds though,....Satan may have a hand in it.

[JDT]

A seal can go bad as it warms up. So if in bought, change it out.

But I would think with the other symptoms you stated that you may have a stator winding problem.

[moontree]

i had similiar problem. CDI fixed it. with CDI it will gradually get worse(will run for less time)

[JD_Sledder68]

Thanks guys! I'll try the CDI tomorrow. If that doesn't do it, I'll order a gasket kit and just tear it down and thoroughly clean/check/reassemble the engine for next year.

Is the Fireplug CDI a good investment on these engines?

[400brian]

Is the Fireplug CDI a good investment on these engines?

There 4 or 5 of us heading up to the VC with new Fire Plug CDIs and rewound stators installed.
Report will follow, but Troy says YES!

[JD_Sledder68]

Well....I went out to the shop to start up the LF and warm it up so I could ohm out the stator....and low and behold: It won't even start. Pulled plugs, laid them on the cylinder head and pulled it over. Good spark to both plugs. Compression is 138(L) and 140(R). So have good compression, good spark. Must be either fuel or sheared key on flywheel throwing the timing off. So to rule out timing, I dumped a thimble of fuel in the spark plug hole and popped the plugs back in. Fired up and then died.

This means either fuel pump, impulse line, or crank seals. I have gone through the carbs already, but I will check them again while they are off to work on the fuel pump.

Should I rebuild the pump or replace it? Aren't these round dual outlet pumps hard to find new?

[harleysportster]

When the crank seal goes bad, this effects the fuel pump and it will stop working. If you do not know the history of any engine rebuild or seal replacement, just replace them anyway.

[nick80lf]

Brian,

I'm not real familiar with the Gen 1 Liquifire, but did the pump look like "D" on this page?
http://www.wps-inc.com/wps/WICATALOG1.p ... 2703835231

FYI, this is Western Power Sports online catalog.

[400brian]

Pretty much. The one on my '78 has a dished top cover, but I would imagine that one would work.
I have always rebuilt them, that way there are no concerns about fittings pointing in the right direction, or anything else. Real easy. I think the pump pictured is off a 340/S.

[JD_Sledder68]

It looks like "D" in the Western Catalog and looks like the one Brian posted. I think I'll order a rebuild kit for it. It looks awful wet around the engine plate beneath the fuel pump. I have been noticing a puddle of oil on the floor when it sits for more than a few days too.

I'm gonna pull the impulse line and test for vacuum at the crankcase while pulling it over before I do anything. It if needs seals, I'll pull the engine this spring and go through it.

[JD_Sledder68]

Well, I took advantage of the warm (58F) day today and pulled the carbs on the Liquifire, blew them out, double checked float settings, pilot jet, etc. All was good, except I noticed globs of what looked like oil floating on top of the gas in the float bowls. Looked like melted butter on top of water. So I siphoned the tank, disposed of the fuel, and put fresh fuel back in it and it runs good again, at least without riding.

While I had the carbs off, I pulled the stator connector and ohm'd out the stator. I ended up with:

Low: 2.76K recommended, mine was 2.57K
Hi: 76 ohm recommended, mine was 75 ohms

When I flushed the tank and replaced the pickup line and screen, I saved the fuel, ran it through a fine screen and reused it. Some of this fuel was the fuel that was in this machine when I picked it up. The only thing that I can figure is that for some reason, the oil that was used in it prior, was reacting with the Amsoil Interceptor that I am using. Now I need snow so I can test.

[400brian]

Mixing mineral oil and synthetic might cause issues, I don't believe it is recommended.

Sounds like you are on the right track.