solex problems

[newto912]

Hi All
have finally got my reg plates, but carbs are playing up.
seemed to be ok driving too and from MOT. not started for a while.
tried to start , very difficult, eventually idling but stalling when accelerator pressed
noticed right hand side exhaust cold.left hot.
I have re checked the valves, it has a 123 electronic ignition, cleaned the plugs- very dark and sooty
took right carb top off cleaned all the jets with compressed air, and noticed no fuel in bowl, replaced the float valve,now RHS carbs has fuel
so start up. I have disconnected the throttle arm linkage to this carb and when the accelerator lever at the carb depressed the engine revs quite nicely, however when just the LHS carb accelerator lever depressed the engine dies , accompanied by phutt phutt and occasional backfire /flame through the carb,
see video
https://www.youtube.com/watch?v=osB1JrqYq7k

any ideas what could be causing this.
I really would like to try and fix myself, rather than take to an expert, as its all part of the learning process and I have come this far.
an I just want to drive her now!!
Thanks for any help pointers in the right direction
Andrew

[SeanP]

Are the float levels correct?
Are the accelerator pumps pumping the correct volume?
Are the main jets clear?

Looks to me that you have an issue with the carb on cylinders 3 and 4

You also need some clamps on the breather hoses etc otherwise you could end up cleaning up an oily mess after a long drive. Please don't ask me how I know

[newto912]

Hi Sean,
1 float levels , don't know as do not have the tool, but have used the straw technique{ Jack staggs of the 912 bbs site) and they are similar in both bowls - or the straw is at the same level in both carbs.
2 don't know about the volume, but it does eject a decent jet when opened -is it easy to measure or does it mean carbs off?
3 all jets cleared by high compression air.

any one have the float tool willing to lend out?

[AndrewSlater]

Hi Andrew,

having battled with my Solex carbs again recently, I would suggest you do need to invest in a synchronometer if you don't have one already in in order to finally set them up properly. As for the float height gauge and the accelerator pump vial you can improvise.

From your straw technique it sounds like the float heights aren't causing your current issue ( but will need to tuned for best performance at some point ).
If you take the carbs back off at any point I would check them on the bench as it is a lot easier.

The problem could also be down to your inlet/outlet valve adjustment.
To rule out whether it is a valve adjustment issue it is generally best to check these first.
To help rule this out you could swap your carburettors over ( you can still idle them and just about get at the arms to repeat your test - but obviously you can't fit the linkages), and see whether the fault follows the carbs or not.

I would also find a way of measuring the accelerator pump volume to at least get into the right ballpark.
A volume of 0.35cc for two pumps is a good starting point and is working well on mine at the moment.
You simply need a small vial that you can get under the nozzle and then a way of measuring it accurately.
Also it is important that the injector stream passes between the butterfly valve and the wall and doesn't hit either on the way. If it hits then your injection of fuel arrives late and not in the correct manner. This isn't particularly easy to verify or correct whilst on the car.

There are plenty of issues that could be causing your symptoms, but too little delivery ( or too much )from the accelerator pump, could be your first problem.

I would be tempted to take off the carb on cyl 3/4 and check the injector pump operation whilst you have it on a bench. If you find an issue correct it and refit. If everything looks OK possibly swap the two carbs over for the purpose of diagnosis.

If the fault follows the carb, you could try changing the jets over from one side to another to see again whether the fault follows.

Just be prepared to spend the time and you will get there in the end.

Good luck
Andrew

[paul lomas]

Scruffy littke car .hi andrew i had to set mine up on the bench in garage ..with fuel holder and a period of 3 nights of adjustment on float heights new fuel has a habit of creaping total crazy you set the float height watch the fuel creep out hole , leave for day adjust again then leave it again ,then adjust it again , simon my mate who got 356 ,talked me through it seems a palava but it works also you got to get your self a balancer its near imposable to set the carbs up with out , took me a good hour of going back and forwards to get it running right and your spot on im from thc same illk i need to know how to fix stuff and how it works , keep it up mate your not far off if your struggling plenty of info on 356 regetry to confuse the hell out off you

[neilbardsley]

I know the solexes are original, and have better air flow, but they seem to be a pain to setup compared to webers!

Sorry I know that doesn't help but try what Andrew suggested.

"I would be tempted to take off the carb on cyl 3/4 and check the injector pump operation whilst you have it on a bench. If you find an issue correct it and refit. If everything looks OK possibly swap the two carbs over for the purpose of diagnosis.

If the fault follows the carb, you could try changing the jets over from one side to another to see again whether the fault follows."

[newto912]

Thanks guys.
then the car failed to start completely!
decided to check compression , cylinders 1- 75,2-90,3- 105,4-125 so I thought compression might be the problem, resigned myself to an engine rebuild.
so engine out, had one more go starting her up and lo and behold she starts! after checking all plugs one was defective
did what Andrew suggested, the fault follows the carb, little fuel in one float chamber, took the head off the carb and one of the springs looks different to the others, also pin on the float height swivle slightly bent, so swapped it all over to the good carb , which has become a bad carb.I think the float probably was not floating properly.
so I think that might be the problem,
accelerator jets all adjusted to squirt 4.5cc per two strokes as per manual
have ordered new bits from Italy and hope that is the issue, if it is then I will put the engine back in and at least drive her around a bit,
does look like I am looking at a rebuild though
toying with that myself??
Neil do you run webers? was thinking about those also, solexes do seem a fiddle
anyone had similar experiences and swopped over to webers?

will report back when the bits arrive

[Mike Smith]

A swap to Weber`s WILL open another can of worms

[neilbardsley]

Thanks guys.
then the car failed to start completely!
decided to check compression , cylinders 1- 75,2-90,3- 105,4-125 so I thought compression might be the problem, resigned myself to an engine rebuild.
so engine out, had one more go starting her up and lo and behold she starts! after checking all plugs one was defective
did what Andrew suggested, the fault follows the carb, little fuel in one float chamber, took the head off the carb and one of the springs looks different to the others, also pin on the float height swivle slightly bent, so swapped it all over to the good carb , which has become a bad carb.I think the float probably was not floating properly.
so I think that might be the problem,
accelerator jets all adjusted to squirt 4.5cc per two strokes as per manual
have ordered new bits from Italy and hope that is the issue, if it is then I will put the engine back in and at least drive her around a bit,
does look like I am looking at a rebuild though
toying with that myself??
Neil do you run webers? was thinking about those also, solexes do seem a fiddle
anyone had similar experiences and swopped over to webers?

will report back when the bits arrive

I bow to Mike's many years of working on these car but yes I run webers on my cars (they came with them). Perhaps Mike can recommend someone local to you to do a check/rebuild on the carbs?

[Mike Smith]

With Weber`s - we always head for the Rolling Road otherwise we spend more time than the customer wants to pay for - It is different if you are not charging your time , you can make a mission of any problem

As to recommending a Rolling road that has become a problem
1 x guy committed suicide
1 x guy died from a dog bite
1 x guy shut his rolling road down
2 x guys I do not trust

Sometimes we have as many problems as you guys trying to find someone who knows what they are talking about

[newto912]

thanks guys
a momentous day!
did some more fiddling , whilst awaiting for the parts to arrive.
anyway got it going and starting 1st time, still phutt phutting, my daughter calls it sputnik which I quite like
been out to Wimborne today , a bit gutless unless revved but its first proper drive- love it and well chuffed
will post a few pics, and also some of the things I have learned along the way

[paul lomas]

Scruffy little car ... bet that brought a big grin to your face , nothing better than bringing a vehical back to life look forward to seeing it the flesh some time

[newto912]

Hi All
well got her quite nicely. had ordered synchrometer to really balance things out, but then something happened suddenly to cause major loss of power and backfiring, nursed her home , took air cleaner off right hand cylinders to find this-

https://www.youtube.com/watch?v=9HWoHAoSpPA

so checked valve clearances again to find cylinder 1 inlet valve spring broken.
gutted was really looking forward to the September meet
looks like my engine rebuild might be happening sooner rather than later!

[neilbardsley]

Well it probably explains some of your idle issues?

What is the history of the engine? Will you have a go yourself? Open the bottom end or just replace the springs and run for a while?

If not there are some good 616 engine builders that advertise on here. PRS are near the top of the list but there is a good wait and I think that maybe the intruder alarm system actives if a 912 approaches the garage doors However, I'm sure that Paul (at PRS) will be happy to sell you some appropriate springs.

[Mike Smith]

Thanks for the plug Neil - we do appreciate it

The moto is - `Always talk to Paul` - he will tell you honestly `the way it is` sometimes it`s good news some times it will make you wince but if you know the truth, then you can plan