Starved for Fuel -1978 70hp

[Doop]

Symptoms - Idles OK in neutral, will not idle in gear for any length of time, just dies off. Full throttle was OK, now it's starting to cut out there too. Squeeze bulb is soft after engine dies, must pump back up. Will not take full throttle from idle unless I hit the choke momentarily and then it takes off.

What I've done so far - Rebuilt carbs, these have no jets just an orifice. I have checked the entire length of fuel line from tank to pump for air leak. Fuel pump has been replaced. When I rebuilt the carbs I replaced all the hoses to and between the carbs. Have had motor for 3 years and always had these symptoms but lately it absolutely will not idle where it used to be just tempermental now it's much worse.

I am convinced this is a fuel issue, so far. One idea I found on this forum is to direct plumb to the engine and not use the connection at the motor housing. I have replaced the connection on the incoming hose but it still wiggles a lot. I will try that. I have also tried a different tank and connector and no change, so I don't think it's an issue outside of the motor. Like I said, it may be the connector. It really acts like an air leak. It could be timing too, I'll check that. Plugs are new.

Anyone have more ideas?

Marc

 

[Chinewalker]

Re: Starved for Fuel -1978 70hp

Hi Marc,
You mention that it has always had some issue with this since you got it. Did the motor by chance come from a different elevation? It's possible that it simply needs a re-jetting to a slightly richer setting.
When you rebuilt the carbs, did you blow out EVERY fuel passage? Removed the plugs and such to access the idle bleed holes, etc.?
- Scott

 

[wavrider]

Re: Starved for Fuel -1978 70hp

Yes you can re-plumb fuel line straight to the fuel pump by passing the fuel quick disconnect, done all the time.

Watch your timing advance and make sure it advances smoothly with no kinks in the movement.

Carbs can be tricky to rebuild, those little passage ways and jets may look clean, but not be all it takes is a particle of trash and you get a lean condition , not good for engine and can cause catastrophic failure if not corrected.

also look at your link n sync on carbs, critical adjustments and can cause poor performance if not done correctly

 

[Doop]

Re: Starved for Fuel -1978 70hp

Scott, I know the history of the engine, it was not from a different altitude. These carbs have no jets to adjust. I removed every plug, soaked carb bodies in cleaner for the recommended time, blew 100 psi of air through all crooks, canals, orifices, etc. Replaced with the new plugs. I did not coat them with any kind of sealent though.

Waverider, everything looks OK in the linkage. I will check the timing advance tonight.

Thanks for the info.

 

[wavrider]

Re: Starved for Fuel -1978 70hp

In rare situations it could be wore out butterfly cam, the shaft the butterfly mount to, allowing air to leak into the carb and messing up the fuel air mirture.

If you get it to idel stick your fingers into the throat of the carb this riches up the mixture and see if it idles better, if it does idle better it is a lean condition and need to look at carb.

also do a compression check, just to see what the numbers are, it may be a bad head gasket, compression check will tell you alot bout the engine and save some headaches chasing a fuel problem when it turns out to be a small leak in the head gasket allowing water into the cyl

calso look at your plugs and se if any lok lke they had a steam bath, sure sign of water intrusion in the cyl.

 

[tashasdaddy]

Re: Starved for Fuel -1978 70hp

did you link n sinc the motor afterwards?