2T-G Twin Solex TUNING help

**Rinmax** · 11-03-2006, 08:37 PM

Well if they have run on a 1800 before then I'd guess its down to the mixtures. Common guys there has to be someone who's tuned these things before.

**RWDboy** · 11-03-2006, 10:02 PM

I don't want to be totally useless ... but you really should try to get it on a dyno, or at least borrow a (edit)mates(/edit) lambda meter (exhaust gas oxygen levels) and do it thoroughly.

The heads are the same between the two motors (unless you've changed the ports or cams etc inbetween) so the flow characteristics of the engine are going to be very similar too - *except* higher up in the rev range where you may be able to flow more air (although maybe not as efficiently).

I've always gone about things by getting the main jets right *first* and then do the secondaries/idle etc (granted i've never touched a mikuni/solex, but it's just how i go about things on other carbies)

Sorry i can't be of more help

**crownv8** · 11-03-2006, 10:15 PM

There is a guy in Redcliffe who is an absolute magician with these setups. He is in Kippa-Ring industrial estate. Can't remember the name, something like carb-tech.

Cheers

**sillycar chick** · 11-03-2006, 10:53 PM

I was planning on finding someone to tune them properly, preferably someone who knows these carbies quite well, but I just want to get them tuned enough to drive around on fairly smoothly until I get the time/can afford it.

**Rodger** · 13-03-2006, 01:14 PM

Sillycar Chick,

I agree it is not easy to get the Solexes running, matter of fact any dual sidedraught set up, as it usually comes down to balancing the two.

I'll try and scan my workshop manual tonight. It contains all the info to set the Solexes back to factory spec and how to balance the two. It uses vacuum guages to do it but the descriptions a good.

Main jetting is typical factory and the main fuel jet would be #130 or #125. Do not worry about the main jetting yet as this will only really come into play when using more than 20% throttle and then as the revs and load comes up. It wont be lean until high in the revs under load which comes latter once some of the running in is done.

The pilot jet is factory and may need to go to #60 or #63.8. If the idle mixture screws need to be turned out more than 3 turns to get the motor to drop to idle, then the pilot jet is one or two steps lean.

Start by checking for loose parts in the carbies, particulaly the inner venturis, worn or broken idle mixture screws, blocked accelerator pump jets, any air leaks into the manifold and then use the manual to get the balance close so it idles.

Here is a quick first up suggestion. It is a fiddle with mixture screws balance and idle speed.

1) Without the motor running, start the initial balance by setting the balance screw so it does not touch the rear throttle arm.

2) Set all four mixture screws to two full turns from closed.

3) Loosen both throttle stop screws until you can feel the throttle plates fully closed. Turn each one until it just starts to open the throttle.

4) Set the balance screw so it just touches the rear throttle arm.

5) Wind the front idle screw up another two full turns and start the motor. Adjust it until it is idling at 1500rpm or so, then adjust the balance so it neither drops or gains revs.

6) Drop the idle back down a half turn at a time until 1000rpm and each time check the balance.

7) If the idle cannot come down to 1000rpm then the rear idle screw may need to be backed off a quater turn or so. Or

8) The mixture could be lean so wind out the miixture screws a half turn to continue to drop the idle.

The motor should idle reasonable smoothly at 1000rpm and drop back to idle quickly and smoothly. Once they are set up spot on after a dyno session the engine should be able to idle well at 800rpm.

The motor should rev cleanly when the throttle is pulled open quickly. This will test the pump jets.

Once you can get it to idle smoothly and not hesitate just off the idle stops (which is another balance check) take it for a drive and in third or forth gear cruise at 2500 rpm. If it runs smooth without missing then the pilot jetting is close to correct and the car can be driven until you can get it on the dyno.

Good luck is not needed but patience is. I can spend hours leaning over a hot enginebay trying to get them to idle smoothly.

Now days I get them set so they dont hesitate or bog down on take off, which is when it becomes unsafe to drive and reccommend the owner takes the car to a dyno to set idle mixtures and balance and check main jetting.

If you need other jets I have them.

Regards

Rodger

**sillycar chick** · 13-03-2006, 04:40 PM

Thanks for the advice Rodger, if I will be repping you when I can do so again

I have passed this info onto my dad who has been playing around with the carbs today while I have been back at work. I think he has been making a few phonecalls as well. I will let you know how it pans out and if I need any jets.

**Rodger** · 13-03-2006, 10:00 PM

I have checked my manual.

I was out on the jet sizing. Factory jetting was Main Air #150 or #180 and Main jet was #125 or #135. The pilot is the same.

So I would be checking the Main jet size at the bottom of the Main Jet Holder. It can be accessed simply by unscrewing the Main Air jet and then the holder.

If the Main jet is the same or bigger than #130 then all will be ok. The motor probably will not pull beyond 4000rpm though but wont be lean to start driving it around.

If it is smaller then the motor is a bit too lean on the main throttle circuit.

If you have concerns then at least you can drill out the small jetting to bring it up to where I would have started, that is #180 MA and #135 M.

My Toyota manual discribes a similar method to set the idle speed and balance as to what I do. I have tried a couple of times tonight to attach a scan of the relavent page, but to no avail my PC is locking up when I select the "manage Attachments" button. I will try tomorrow at work if you still require.

Regards

Rodger

**allencr** · 14-03-2006, 02:03 AM

Don't even think about changing jets until the carbs are in sync - carb to carb, and that's after getting each carb's throats equalized if they're off.

Just listen to the hiss from each one AFTER you know everything ELSE on the engine is equal & OK - compression & ignition. Don't just assume it is a carb problem.

It is definitily not necessary to have a Unisys or monometer or anything else, other then a piece of tubing, to find out if the throttleplates/butterflys are in sync.

**sillycar chick** · 14-03-2006, 09:05 AM

Originally Posted by Rodger

I have checked my manual.

I was out on the jet sizing. Factory jetting was Main Air #150 or #180 and Main jet was #125 or #135. The pilot is the same.

So I would be checking the Main jet size at the bottom of the Main Jet Holder. It can be accessed simply by unscrewing the Main Air jet and then the holder.

If the Main jet is the same or bigger than #130 then all will be ok. The motor probably will not pull beyond 4000rpm though but wont be lean to start driving it around.

If it is smaller then the motor is a bit too lean on the main throttle circuit.

If you have concerns then at least you can drill out the small jetting to bring it up to where I would have started, that is #180 MA and #135 M.

My Toyota manual discribes a similar method to set the idle speed and balance as to what I do. I have tried a couple of times tonight to attach a scan of the relavent page, but to no avail my PC is locking up when I select the "manage Attachments" button. I will try tomorrow at work if you still require.

Regards

Rodger

Thanks Rodger, this is all very good stuff! If it makes things easier you could email me the attachments and then try to post them up for everyone elses benefit later....?