Engine will only run above 4000 RPM. Carbs or timing?

[pacemkr]

just a quick thought? maybe it will help someone else think of something a little more practical//

but, any way the vac advance could be activating too early.?

try unplugging or pinching off the advance tube and turning it over.

[Wade Nelson]

Have you checked that all three throttle butterflys are inter-connected and operating properly? I know that probably sounds stupid, but...

[Zed Head]

The oil pump shaft is where it should be and the distributor is in perfect position.

I'm ruling possible timing issues out from here on, I've explored them extensively and it all seems to be in order.

You didn't mention what the timing light showed. Just for the record.

[madkaw]

Zed,

Don't see how he can get a timing reading the way it runs

[Zed Head]

Actually, I think that timing at 4,000 RPM would tell something. If you know your advance curve, and disconnect the vacuum advance, you could calculate initial.

And with a good light I think that you can get timing just from cranking. Or a better way to guesstimate initial timing is to look at where the points open, or the rotor passes the pickup coil or the led gets blocked (or unblocked), rather than distributor rotor position. That doesn't tell anything about timing, since the it doesn't tell where the distributor body is positioned.

When you have no clue, you can't rule anything out is the essence of my post. Things should be more clear after 87 posts than "revving to 4,000 RPM is the only way to to keep it going". What good will a vacuum reading at 4,000 RPM be?

No offense intended but a methodical approach would help get to a solution. Get good solid basic information and a path will become clear. This thread is jumping all over the place.

[madkaw]

Wouldn't rule out demon squirrels in the crankcase right now -

Just think trying to get a timing reading with it running so erratic would be tough with one person especially .

Chris,

You didn't run the SUs with one fuel line did you?

That large vacuum line is now going to your gauge instead of the booster?

[bartsscooterservice]

Thru the regulator set at 3.5 I'm getting 1.5 Litres per min(I tested it with a jug and stop watch).

Fuel flowed at a nice steady stream. All bolts are tight.

If I take this to a shop to fix they are going to rape me and I'm not sure they are going to figure out either.

I've checked every system a dozen times. How does an engine pull enough fuel out of a carb to race it up to 4-5000rpm without touching the pedal?

What fuel pump where they running on the triples when you tested the engine before buying it? What did you change to the engine in your car? The fuel still okay quality?

Edited May 7, 2013 by bartsscooterservice

[Travel'n Man]

Do you have the vacuum advance hooked up? I do not have that connected with my Mikuni's.......

[grannyknot]

just a quick thought? maybe it will help someone else think of something a little more practical//

but, any way the vac advance could be activating too early.?

try unplugging or pinching off the advance tube and turning it over.

I had the vac advance plugged with triples and with the SU's I've had it with a hose to vacuum and plugged, it made no difference. It's plugged at the moment and will stay that way, one less variable.

Have you checked that all three throttle butterflys are inter-connected and operating properly? I know that probably sounds stupid, but...

When the triples were on all the butterflies were in sinc.

The SU's butterflies appeared also to be in sinc before I installed them.

You didn't mention what the timing light showed. Just for the record.

Just cranking the timing mark on the pulley is about at 10* with the timing light.

Zed, your right it is all over the place, but people make a suggestion, I go and try it and report back, any one of them might be the fix.

Wouldn't rule out demon squirrels in the crankcase right now -

Just think trying to get a timing reading with it running so erratic would be tough with one person especially .

Chris,

You didn't run the SUs with one fuel line did you?

That large vacuum line is now going to your gauge instead of the booster?

Demon Squirrels...THAT'S IT!

fresh fuel going to both carbs, and yes that is a new hose and it's feeding the vacuum tester.

What fuel pump where they running on the triples when you tested the engine before buying it? What did you change to the engine in your car? The fuel still okay quality?

I don't know what fuel pump he was using but the 1.5L per min. pump that I have now is enough for an idle.

What has changed? He had a header on I have a bored out cast iron exhaust manifold, he was using a generic HEI module and a Bosch coil, I'm using a matched HEI module and coil from Pertronix. He had the triple carbs which I tried extensively, but spark plugs were always wet and fuel spilling out the front, since installing the SU's no wet plugs and only a bit of gas coming out the front when it back fires through the carbs on shut down.

A little success today, I managed to get a very rough and low idle out of it twice, each time only lasted about 10 seconds and the timing light showed pulley mark at about 12* In between those 2 attempts were lots start and die immediately and the usual start and surge up and down like in the second vid. I changed nothing between these attempts as I was trying to get a reading with the timing light.

Chris

Edited May 7, 2013 by grannyknot

[madkaw]

Okay-here's a thought. You say you changed exhaust.Now you know it's imperative that the the flange thickness on the intake and exhaust are equal. If your 'new' exhaust for some reason has a thicker flange--- then your intake is not getting torqued down properly and causing major vacuum leaks along the bottom.

[Wade Nelson]

What about a blocked exhaust. Above 4000 it may be able to push through enough exhaust to run. Try cracking the down pipe and see if anything changes...

[pacemkr]

grannynot,

im waiting on tires that are back order. so i cant drive mine at the moment.

mine is running well now. could you make use of my coil or anything for trail purposes?