hs2's slight hesitation under load

[Woodie]

OK today I got the front carb changed out. It seemed to run fine. After dinner went for a short run. It seems there is some hesitation under load when just starting in 1st gear, it also seems not as smooth when lifting the foot of the gas to coast in 3rd and 4th. With the changes made to vacuum and the carbs any suggestions. ?? When I pull the choke out about 1/3 even when warmed up it smooths out.....

 

[Baz]

Air leak on the intake?
Is the rear carb out of whack from changing the 1st?
Definately sounds air related....

 

[jlaird]

Are they balanced properly?

 

[Woodie]

OK here is an thought, while driving to work today. The car started fine, with choke full out, it idled at 2000. After a minute or so I pushed choke in half way. Still idled fine but now about 1500. Pulled out of driveway. A bit hesitant. For the nexty five minutes to avoid the bucking bronco syndrome I pulled the choke full out. At least I could pull away from a stop sort of smooth. Once fully warmed up, with choke in all the way, from a smooth idle of 1000 when I step on the gas until about 2500 rpm she just wants to die. Once past that point she goes like stink, pulled onto the hiway and hit 70 real quick. There is much more power there now than yesterday.

Anyway my thought, I believe when filling the dashpot on the rear carb last time I used 10W30, yesterday when setting up the new carb I used 20W50 (use that in the engine) I am going out at lunch time to remove and rain both pistons and refill with fresh 10W30 or maybe marvel Mystery oil, (any preferences folks??)

I do not believe I have any air leaks cause when I sprayed carb cleaner all over the carbs yesterday the idle did not drop and stall the car out. (actually I think the idle actually increased a bit ???) So I will try the change of oil, and see, otherwise I guess I need to re balance the carbs,,,,(yup yup 12 flats out and 2 full turns on the idle screw, start and adjust)

 

[Baz]

[ QUOTE ]
(actually I think the idle actually increased a bit ???)

[/ QUOTE ]

If the idle picks up, that would be an air leak, however, I also think 20W50 may be a too heavy also. I have lightweight oil in my pots.
The bad news is, I think you'll have to balance anyway.

 

[Woodie]

Hmm well I just re read the Su tuning manual, and they say that the back firing that I am experienceing (uneven and such is caused by a weak mixture. So that combined with to thick oil and I amy sort this out at noon. I'm gonna check the little push pin things under the carb. Lift the piston a bit and if she dies out to rich, if she idles faster too weak...

 

[Trevor Jessie]

...and be sure that the air cleaner back plate is no upside down. But it sounds like an air leak. Tighten things up and then set the mixture.

 

[Woodie]

True Jessie True,, I had the plates upside down once before, I will also tighten the carb to intake bolts, the choke shaft nuts, and the throttle shaft nuts. Then do the oil, try it, then adjust as necessary. I'll let you guys know. Thanks

 

[jlaird]

Your problem is without question carberation, for crying out loud take 5 min and adjust and balance the carbs after insureing that you have no air leaks.

 

[Woodie]

Thats what I'm going to do Jack, I'm going to check for leaks, change the oil and re-adjust and balance the carbs I also have to balance a working wife a 4 yr old son, my job, and the car. I worked on the car for 4 hrs yesterday afternoon. Then spent the rest of the evening with my son till 9:30 PM while my wife slept before going to work at 11Pm. So I had 1 1/2 hrs with her. I left for work at 6:30 am..and am here till noon. Then I will go out and get my hands into her for a while. rest assured I do what I can when I can, and I do appreciate you and the others being patient with myself and other rookie car mechanics. I am sure my car would not be running with out your help or lots of cash. I am a proud Midget owner. I love my car. I am unsure of what to do so I try to describe issues here so I can get ideas on where to start. So far this boards help has been supurb, I am constantly amazed that problems (not just mine) can be described diagnosed and fixed with a BBS. oh, and Jack just to let you know, I am working ILS and maintenance issues for the Canadian Navy Submarines (civvy contractor) so being carefull is job trained, maintaining dive certificates is as important as Airworthiness. So I kinda carry that look before you leap into what I do with the car, approaching everything slow and with lots of input. Again thanks and please keep up the great work on this board

 

[Trevor Jessie]

I think you know, but it may be necessary to adjust the mixture and balance several times if they are way off. In your case, I'd start with the mixture, then balance, then mixture again if needed. Then final adjustment on the mixture with the air filters in place. Then set your idle.

 

[leecreek]

changed one carb? Did you check for match of needle and spring?

 

[Woodie]

I put the old housing and piston with spring and needle on the replacement body. So same same. The needle is centered as well. with no load the piston rise almost at same speed it only faulters under load....

 

[Morris]

Hey Woodie,

I have been following your thread, and I have a concern about how you set up your spark advance. I don't have a lot of experience with the 1275 set up, so take this advice with a grain of salt...

Because on your old carb, the tube for the advance was coming from the carb, that makes me think that the advance is supposed to be ported. This means that the advance gets no or little vacuum at idle. Vacuum is applied as the throttle opens up. If you are getting backfiring on deceleration, it may be due to an overly advanced ignition. In other words, if your advance is meant to be ported, when you let off the throttle, your spark should be getting no advance. But since your advance tube is plugged into the manifold, you are getting way too much advance and your spark is hitting while the valves are still open causing a backfire.

It's never a bad idea to check for vacuum leaks and balance the carbs. But as an experiment, you may try plugging your vacuum advance, checking your ignition timing, and givin' her a test drive with the advance plugged.

 

[Woodie]

Morris I love salt... Thanks, I will take the vac hose of the intake and take her for a short spin to warm her up so to speak, see how it drives. If no change then I guess I go ahead and do the other stuff. If however there is improvement, what do I do about dizzy vacuum advance,? Can I leave it plugged or not or should I find a new source of vacuum. If you look at this picture, you can see the vacuum hose to the dizzy of the carb, behind the butterfly. I moved the hose to the port on the intake (where the philips screw was. )

 

[Trevor Jessie]

OK, I've been trying to decide why the DPO changed only the front carb. Maybe it was because he needed a ported vacuum source to go with a distributor that is not original to the car. I'd test as Morris said, and if it solves the problem then I'd look for a correct distributor with an advance curve better suited to your engine.

 

[Woodie]

oh, ok Trev, thanks. I am on my way out to test the car etc etc now. Be back in about an hour or so and will report on my findings/results... Wish me luck....

 

[Woodie]

Well I removed the vacuum to the dizzy and plugged it, car would not run, stalled out, Blah. So back on it went. I removed air filters and it is the front carb that when gas is given it sputters and dies. I leaned it way out, same thing. So I tried the other way, rich, about 3 or 3 1/4 turns, seems to have solved or almost solved the issue. I took a short run, with 3 stop starts or so and the hesitation is gone. The idle is a bit high, but I can turn that down quick enough. But the car does not drop back to idle quickly?? I can't hear any air leaks, I had no spray, I will check again at home tonight, but I tightened everything up again.

 

[jlaird]

Hmm, I still say work on balanceing and getting the carbs adjusted. No question in my mind.

 

[Woodie]

Oh I agree Jack, I figure a hour or two of trial and error, or goto the local LBC mechanic and give him $50 buck to do it.....but where the satisfaction in that eh?? (Can you tell I'm Canadian) Which brings me to the subject of Beer,,Im still at work and get have one for a while yet