idle is still rough.

[Stupid_fast]

I think I suck at adjusting valves. I spent some time on them while the motor was hot, the valves are a lot more quiet now and its running better but not perfect.

 

Idle is still rough, I think its a matter of fine tuning out every small problem.

 

 

The hesitation is still there... I'm wondering if rejetting the carb would solve this or if I should just grab another carb?

[Stupid_fast]

I think it is the carb at this point, I've fixed every other possible problem with mechanics of the engine and ignition.

I found one small vacuum leak on a plugged PCV valve, replaced it with a bolt and a runs a little better.

 

I notice if I hold the throttle barely open, like 2-3% it will be more rough than idle, but more on the throttle and higher RPM will be normal.

 

If I open the 2nd throttle(by hand) from idle, it is not rough like doing the same with the first... This seems strange to me.

 

The main thing that is annoying me is the hesitation, engine breaking, coming to a corner, foot on break, clutch in, lower gear, blip throttle and it just hesitates... Wont rev up unless I do it gently.

 

Can float setting cause hesitation?

 

 

 

[Stupid_fast]

I thought I'd just bump this rather than creating a new topic.

 

So I got a jetting kit for the 32/36 as I would like to get it running decent before I start really modding.

 

At first since the plugs kept getting blankened/carbon fouled after a while I thought the carb was probably too rich, so I lowered the primary jet from 140 to 130, this made it run worse hesitation was terrible to the point I could barely get going from a stop.

I pulled it back apart and upped the jet sizes, put the primary's at 150-180 and now it runs a lot better, after that I decreased the primary air corrector from 160 to 150, which made it run even better.

 

Current jetting has ended up at(with only tweaking it a few times),

Primary's 150/180

AIr corrector's 150/170

Idles 60/50

 

 

There is less hesitation, better response and power through the whole rev band, but this does not make sense to me as it seems like really large jetting for an L20b. It sounds and smells like its running really rich. Anyone got any more ideas or tips for me to try to pinpoint this problem? I've turned my attention back to the ignition system but I don't know what else I can try.

 

The main problem is the carb leaning out under some conditions, I went 2nd gear WOT to 5,000 RPM, 3rd- 4th going uphill holding at like 4,000 rpm for about 10 seconds, went off the freeway and it would not idle. It kept leaning out and dying, it does this sometimes on hills, while braking, coasting to a stop, ect. Ideas? Now that its rejetted it usually does not stall anymore but its still not running right. Has a hard time revving up for downshifts if I'm not careful.

 

I've pulled out the carb a few weeks back and completely blasted it out with carb cleaner... reassembled and no change.

 

I ordered a few sets of cheapo NGK plugs to replace the fouled out ones(gone through 2 sets of $7 plugs already).

 

Thanks.

[datzenmike]

Do you have a stock cam in there? High overlap cams have terrible manifold vacuum and that causes low speed/idle problems that quickly go away when revved up. Borrow a vacuum gauge... you should have 18 inches or so at idle. Try turning down around 700 and see what you get.

 

Try removing the large hose to the brake booster and plug the manifold pipe. Did that help? Could be leaking brake booster or hose.

 

Timing: Static timing is 12 degrees without any vacuum or centrifugal advance. There shouldn't be any vacuum advance from the carb at the proper idle setting (650-750) If you set the timing with the hose attached and idling at 1,000 there may be vacuum advance and it will be set way too low. When you turn the idle down the vacuum is removed and the distributor will retard. All motors want and would like more advance at idle (14-16 degrees) but smog carbs are designed to not supply vacuum at idle. The problem is you can't just dial in an extra 4-6 degrees because when the throttle is opened the vacuum advance jumps it up way too high and it pings. Try reducing the idle to 700 and pull the vacuum advance hose off just to be sure. Check the static timing is 12 degrees and connect the hose... the timing should not change..

[az_rat210]

Based on what you have said. The motor runs well, pulls hard, runs hard and the description about almost dying sometimes and other times not means one of two things to me.

 

1) Low Float Setting

2) Or if you are running a fuel pressure controller, the pressure may not be high enough to keep the float bowl full when you punch it causing momentary starvation. (I had a similar issue when running my fuel pressure at 1.5 lbs instead of 2 or 2.5).

 

Check those.

[datzenmike]

The only problem with that theory is why does it run fine at high speeds where the demand for fuel is at it's highest but baffes out at idle or going around corners?

[az_rat210]

Good Question Mike,

 

I had missed this part.

 

The main problem is the carb leaning out under some conditions, I went 2nd gear WOT to 5,000 RPM, 3rd- 4th going uphill holding at like 4,000 rpm for about 10 seconds, went off the freeway and it would not idle. It kept leaning out and dying, it does this sometimes on hills, while braking, coasting to a stop, ect. Ideas? Now that its rejetted it usually does not stall anymore but its still not running right. Has a hard time revving up for downshifts if I'm not careful.

 

Looks like he took car of the stall issue with rejetting except on downshifting but it still sounds like starvation (thats why I suggested the float level or fuel pressure, as it was so condition specific).

 

Be interested to know exactly what fixes it besides a carb replacement, that shouldn't be needed.

[Stupid_fast]

Do you have a stock cam in there? High overlap cams have terrible manifold vacuum and that causes low speed/idle problems that quickly go away when revved up. Borrow a vacuum gauge... you should have 18 inches or so at idle. Try turning down around 700 and see what you get.

 

Try removing the large hose to the brake booster and plug the manifold pipe. Did that help? Could be leaking brake booster or hose.

 

Timing: Static timing is 12 degrees without any vacuum or centrifugal advance. There shouldn't be any vacuum advance from the carb at the proper idle setting (650-750) If you set the timing with the hose attached and idling at 1,000 there may be vacuum advance and it will be set way too low. When you turn the idle down the vacuum is removed and the distributor will retard. All motors want and would like more advance at idle (14-16 degrees) but smog carbs are designed to not supply vacuum at idle. The problem is you can't just dial in an extra 4-6 degrees because when the throttle is opened the vacuum advance jumps it up way too high and it pings. Try reducing the idle to 700 and pull the vacuum advance hose off just to be sure. Check the static timing is 12 degrees and connect the hose... the timing should not change..

AFAIK the cam is stock, then again I don't know anything about the motor besides the fact it was rebuilt. I will measure the cam and see if it is stock.

 

There is no brake booster.(ha, who needs power brakes anyway?)

 

I was busy helping a friend with headgasket over the weekend, I will check the timing like you described tomorrow.

Timing was last set @ 15btdc at 1000rpm w/ vac advance plugged.

 

Based on what you have said. The motor runs well, pulls hard, runs hard and the description about almost dying sometimes and other times not means one of two things to me.

 

1) Low Float Setting

2) Or if you are running a fuel pressure controller, the pressure may not be high enough to keep the float bowl full when you punch it causing momentary starvation. (I had a similar issue when running my fuel pressure at 1.5 lbs instead of 2 or 2.5).

 

Check those.

Float I've tried adjusting it many, many times and have found the best setting is weber spec of 35/41.

 

Fuel pressure I have no idea, I still have to get a FPR and gauge.

Pump is new(3000 miles by now) Kyosan.

 

The only problem with that theory is why does it run fine at high speeds where the demand for fuel is at it's highest but baffes out at idle or going around corners?

Good Question Mike,

 

I had missed this part.

 

 

 

Looks like he took car of the stall issue with rejetting except on downshifting but it still sounds like starvation (thats why I suggested the float level or fuel pressure, as it was so condition specific).

 

Be interested to know exactly what fixes it besides a carb replacement, that shouldn't be needed.

Yes it runs fine higher RPM with deeper throttle, can get on it while passing on the freeway like 4000rpm wot no problem.

Drives nice cruising speed 3500rpm ~70mph no matter how steep the hill never have to downshift.

 

Stall issue is still there, its just improved a little by rejetting. I'm still trying to figure out a pattern to when it does it. It seems random to me right now!

 

I am also interested in whats causing this, I want to figure it out before I swap a new carb setup!

 

Also when driving to help my friend this weekend, like 80 miles freeway when I got there and driving around town it started running badly, didnt want to idle well, really rough, ect. Before I took the freeway home I found the timing had been advanced a ton(even though dizzy was at the same position when I timed it last!). I retarded it a ton tuned by ear and it ran great, less stalling ect got home fine. I still have to dig in and figure out what caused it to get so advanced.

 

Thanks for the help, I will time it more accurate tomorrow and try to find out more.

[banzai510(hainz)]

I noticed my 8mm bolt holding the timming plate to the dizzy was loose thus changing my timming

[Stupid_fast]

I noticed my 8mm bolt holding the timming plate to the dizzy was loose thus changing my timming

 

Nope, both of em where tight. That happened to me before!! I made sure it didn't happen again... I always get it nice and snug!!

[ggzilla]

When a carb is in good shape, hesitation on acceleration is primarily due to to the accelerator pump settings. You can rich that up without changing the main jetting. The main jetting should be sized for steady state cruising (not acceleration).

 

The Weber DGV (32/36) use a positive diaphragm type accelerator pump, so it shouldn't have 'intermittent' problems. So the mystery continues.

 

Remember an L20B takes the same air/fuel ratio as a VG30 or an A12. The jetting is nearly the same with stock builds. The most important jetting differences are due to the air volume that's flowing (air flows faster than gasoline) so things like accelerator pump settings and transition points need to be adjusted for perfect mixture control. The 50mph cruise (main jets) will be the same or near the same for all.