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Carb Icing AGAIN!!!

45K views 21 replies 10 participants last post by  Ronaldo 
#1 ·
Just need some advice really

I've has my bug for 3 years and have always had probs with the solex carb, it'll run fine for a few months then start playing up again, had it rebuit and cleaned out twice and had my heat risers unblocked a couple of months ago but now the weather's getting a bit chilly again I've found he's coughing a bit and there's condensation on the carb again and it's icy cold

So! now I've decided the carb has to go and I need suggestions of what to fit instead, I had thought about a single progressive weber but have read bad things about them, the engine is only a 1200 with 73000 miles on it so don't know if it's worth fitting twins to, but there's no end float, it's the original engine and pretty much in good nick, don't really wanna fit a new solex cos they have a reputation for being crap don't they

Any suggestions?
 
#5 ·
I dont think teh solex carbs are seen as shite?

If the carb is set up properly, theres not much that would beat it IMHO on a standard set up. Risers unblocked and connected to exhaust, carb cleaned and rebuilt... are you useing the original oil bath filter or an after market? My carb started icing when i changed filters... dunno why, cant see why... just did.

Besides that, i'd go for the IMDU myself... any other carb would probably do the same.

Chris
 
#8 ·
To clear up any confusion - the progressive will Ice up just the same - its a single carb in the middle a long way from the heat of the heads

Cleaned out heat risers, IMDU and an air intake that takes in the warm air from beneth (plus the flap on the oilbath intake to force the use of the warm air)is the whole shooting match

See if the IMDU fixes it now

JAmes
 
#10 ·
Stick with the original carb. If everything is set up correctly it will run perfectly, it's just not many people know how to do it. Post or mail me a good clear pic of your engine bay and I'll show you what to do. Even tho' you've has your manifold cleaned have you tested to see if it's getting hot? and is the carb pre-heat air supply working? What's the number on the left side of the carb?
 
#11 ·
Moby is talking sense again. There is nothing inherently wrong with the solex carb set-up on a 1200 so you should not have to change to an alternative. A cleaned pre-heat pipe does not mean it will be functioning. Firstly, it may not be completely clean, just a little unblocked. Also, it only works properly if the exhaust and tail pipes are fitted correctly. Do you have a standard exhaust? If you do, is it one of those aftermarket ones that simply wont allow the pre-heat pipe to work? On my 1200, the pipe got 'skin-burn' hot within minutes of starting the engine.

Don't go back to the IMDU because, as you said, they are only a temporary fix. The cars worked fine without them and there use only promotes bad engine practice (duck!). If you keep an accurately maintained and tuned full standard 1200, you can out perform many 1600 drivers, who think their hot!
 
#12 ·
I'll try and post a pic of my engine bay, I'm sure I've got one somewhere, maybe my carb just hasn'r been set up very well, Lion Garage in Loughborough did it last when they cleared my heat risers about 6 months ago.

I must admit tho, he seems to have got noticably worse since they had my engine out to fit my new flywheel oil seal last week, you think maybe something's not been put back properly, and if so, where do I look??

No that wasn't me at Broughton Astley crossroads, I don't go that way and he hasn't actually stopped yet, he just kicks a bit on start up, jerks a lot on accelleration and refuses to tick over for about the first ten minutes of driving.

I've put the flap down on the air filter which seems to have helped a bit, the carb's not getting condensation on it anymore but it's still quite cold.
 
#14 ·
Thinking aloud...

Ideally you'd want the dynamo out of the way and with a bit of wiggling about youll get the rubber bungs off and the fanny moulds out of the way...

If you bet be £250 I couldnt do it - Id do my damdest - but if it was me and pre-ferrable in the splitty..... Id drop the engine and do a couple of other jobs at the same time - like fit the thermostat flaps that are sitting on my garage floor but should be helping my engine get up to temp quicker....

What does everyone else reckon?

James
 
#16 ·
If you can get to all 4 tinware screws on the dynamo plate it will pull forward and out - but going to be a bit fiddly

James

fastfugitive said:
I've tried before - its a right PITA...
As you say, you need to remove the dynamo, which means you need to remove fanhousing etc. etc.

PITA!

Quicker and easier in the long run to remove the motor and do it properly with full access to everything!
 
#17 ·
Cheers for all your help chaps, I seem to have cured the problem, the flap on the air filter kept opening again while I was driving but I've stopped it doing that now, also the hose from the exhaust to the air filter was letting in some cold air cos it wasn't fittting properly at the exhaust end so I stuck a jubilee clip on it and fingers crossed, he's running sweet again!

Thanks again. :)
 
#19 ·
On oil bath air filters there is a flap just inside the air intake operated by a cable that you can either have open in the summer or closed in the winter to stop the carb getting too cold. On mine the cable disappears into the body but where is goes from there I aint got a clue so I've just developed a way of jamming it closed when I need to!
 
#20 ·
kiaora said:
what is that flap on the air filter ? and where does the cable that operates it go ?
The flap regulates the amount of hot air that is draw into the carb from the exhaust during warmup. When the engine is cold the flap directs hot air into the carb from the pre-heat pipe. If it has a cable, it is operated by a lever on the front of the fan housing that is connected to the thermostat under the right hand cylinders. as the engine gets hot the thermostat expands and opens the cooling flaps in the housing and also the flap on the stock air filter.

Older filters don't have a cable operated flap, just a manual one that you close when the weather gets cold.
 
#22 ·
"Older filters don't have a cable operated flap..."

Other methods of flap operation are a weighted lever which is overcome by the volume of intake air. Flap opens to provide ambient air at wide throttle/high engine speeds, but still provides heated air to a hot engine at idle. Also a rather neat thermostat adjacent to the flap mechanism itself rather than the fanhousing flaps thermostat.
 
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