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Old 12-10-2008, 08:26 PM
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Default VW trike carb icing

Any of you guys have the same problem as me with carb inlet manifold carb icing causing shitty running, etc on VW trikes cos of the long inlet tract of single carb setups?

Common problem on these engines, especially so on trikes cos engine in full airflow and dont run original oil bath air filters with heater flaps, etc, etc. Happens mostly when sit at 70+ mph for a few miles, then starts cutting in/out and wanting to die. Carb inlet just below carb is soaking in water or white with ice. Below that is heated by exhaust hotspot tubes which feed hot exhaust air up through a manifold.

Basically I need to sit below 70mph all the time. Not happening up ere with the empty roads., or just use it in the height of summer..........err no. Like to use it all year round but starts carb icing at not even 60mph in colder weather which is a right pain in the arse cutting out every few miles. Twin carbs sorts the problem as shorter intakes, but 1 carb setup I prefer and getting 40+MPG out of her at mo which I wouldnt get with twins. No money for new carbs anyway.

Looking at buying a IMDU which is a wee electric blanket that wraps round the top part of the manifold and is meant to stop the problem. Anyone had any experience with these before I spend out on one (30-40) ?
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Old 12-10-2008, 10:15 PM
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they do work
but so does some 6mm copper pipe tapped into an exhaust header, wrapped around the upper manifold you can tap it back into a silencer
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Old 13-10-2008, 01:30 PM
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Interesting idea.

Had thought to do a similar setup using one of those sandwich plate oil take-off plates under the oil cooler and feed warm engine oil round tubing. Exhaust setup probably lot easier n cheaper tho. Just didnt think the small tubing would feed the heat that distance.

Should be able to source some brake line n fittings locally, even here.
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Old 13-10-2008, 01:49 PM
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I've used the IMDU with fairly good results, are u running the pre heater pipes from exhausts(part of inlet manifold)? if they are blocked the carb will ice up, I used an old clutch cable on end of a drill to unblock mine (careful not to jam cable once ur passed the bend in pipe!) or heat em up wiv oxy/acet an giv em a wack wiv a hammer (gently)
Best option go for a set of twin carbs better performance an if set up right better MPG, dont go for the empi copies of the weber 34ict's as they are total crapp.
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Old 13-10-2008, 01:52 PM
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as a quik remedy u can run a piece of that flexible corrugated pipe they use on standard beetle engines (goes from heat exchanger to fan housin) I lock wired one end to exhaust pipe an other end to outside of air filter made things a bit better an only takes 2 mins..
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Old 13-10-2008, 04:17 PM
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No dosh for twin carbs at mo. Standard setup returning 40+mpg at mo n would prefer to stick with single carb anyway tbh.

Cheapest Ive found IMDU`s is 32.77+vat+PnP so far. Copper pipe idea seeming like best bet really as cheap to do and a permanent fix which I need as use it all year round.

Just wanna get it sorted before rebuilding trike over next couple of months. Might take the copper pipe take-offs from the pre-heater pipework so less distance for air to travel. Pre-heat pipework clear n scolding hot, just doesnt get top section of inlet manifold hot enough as cold airflow cools it too damn quick. Is getting cold up ere now tho.
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Old 13-10-2008, 04:51 PM
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Local tuner did say that usin a slightly bigger main jet can help with icing up problems at higher tevs, aint tried it meself tho..
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Old 14-10-2008, 04:57 PM
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Bought some copper tubing today for couple of quid. Tapped into pre-heater pipework. Started it up n first few inches of pipework scolding hot. Great thinks I. Got 4 miles before it cut out!

First 8" or so of copper pipe very hot, but copper/brass dissipates heat too damn well so by time it comes to copper coils round carb manifold theyre cold to luke warm at best even after 20 minutes+ running. Had to drive home in 2nd gear as anything over 40-odd and it was icing n cutting out again. It is pissing cold out there tho right enuf.

Back to square 1 again. I`ll re-use the copper tubing again for something and the 2 holes will vbe easily sealed up again. Might have to invest in an IMDU after all as doing my head in.
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Old 02-11-2008, 01:38 PM
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Got it sorted in the end. Blocked off the filter element n fed 3 old large bore oil lines I had lurking in a box down to a scrap bit of random alloy I had lying about. Drawing warm cylinder air nicely. Just been out for 20-odd mile blast. Sat at 80-90-odd on straights n generally thrashed arse off it. Got 3 wheels off the ground over a humpback hill past the church. God I love sundays round ere. Was bloody cold out there. Cant be more than couple degrees above freezing, but no probs whatsoever. Didnt miss a beat.





Cheers for suggestions n hopefully these pics are of use to anyone else with similar problems. Working perfectly!
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Old 19-11-2008, 10:42 PM
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Quote:
Originally Posted by harris View Post
Bought some copper tubing today for couple of quid. Tapped into pre-heater pipework. Started it up n first few inches of pipework scolding hot.
I know this post is a bit late but I followed a link form the workshop. Cooper pipe has worked in the past but to get round the cooling at speed we ended up using plenty of exhaust wrap which stopped the heat from being wicked away.

It was done on an old beach bastard which had an exposed lump so I don't see why it shouldn't work on a Trike.
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Old 20-11-2008, 09:31 PM
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cheers mate thanks for the info
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Old 20-11-2008, 10:26 PM
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I buy 100% alcohol from the chemist which is called 'ISOPROPYL ALCOHOL'
This I put into my tank as I run with a carb. Winter only for helping the carb not to freeze.

Now called Propan-2-ol, and often available on ebay.

http://cgi.ebay.co.uk/IPA-Isopropyl-...em250290049003


Just want to put the record straight on carb icing as there a few myths floating about.

Carb icing can occur at air temperatures between 0 decress and 23 degrees Celsius.

It cannot occur at temperatures below freezing.

Carb icing is worse in high humidity conditions i.e. Fog.

Carb icing is actually ice crystals forming in the low pressure areas of the carb, i.e. the venturi. Those of you who paid attention at school will know that when you put a gas under pressure the temperature will increase. Conversely when you drop the pressure of a gas the temperature will decrease.

This is whats happening in your carb. At low cruise throttle openings or when the engine is on the overrun, the pressure in the venturi drops. The drop in pressure will result in a drop in temperature. If the drop in temperature low enough and is sustained for long enough, ice cystals will form. These are what makes the bike run rough and in extreme cases will stop the engine.

Petrol additives won't help as these just stop the petrol freezing. The ice cystals don't come from the petrol, they come from the air and there's nothing you can do about that!

Piston engined aircraft suffer from this problem a lot and they get around it by directing warm air onto the carb. Other methods are electrically heated jackets or heated elements using warm radiator coolant.

The design of the carb and inlet tract are the main contribution to carb icing which is why certain carbs and air boxes are more prone than others. For info, Fuel injected engines don't suffer from carb icing at all.
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  #13  
Old 12-12-2008, 07:38 PM
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Default problem solved !!!!!!!!!

HI GUYS..
Just joined ,,enjoying the "craic"... my own 1300 VW had carb freeze
when I got it ...still had original air box, so i fitted flexi ally hose x 2" to air box onto a saddle clamp on bare exhaust pipe with air holes to allow enough air in...the WARM air was enough to fix it ....did road test in similar conditions
wet/ misty/ cold/ and never had no more probs....also fitted ignition kill switch for safety,,,,
like the forum ...plenty tech hints...stories...and info .......looking
forward to more.....
keep in touch
RICCO... A.K.A ....the CUILLINS COWBOY...

PS I LIVE on the ISLE OF SKYE ,,,, drop in sometime !!!!!
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  #14  
Old 13-12-2008, 07:17 PM
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Smile not carb icing but help me please

im new to this trike stuff but i have recently brought a vw rolling chassis trike for my father inlaw for the summer engine is still on beetle rear end but im not sure of how to wire it up just to test the engine i have no fuel lines on at present of fuel take is there a way i could rig it up just to get it to fire brought new dizzy leads and i havnt fitted a regulator but i have got a new one when it comes to electrics im a bit stupid
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Old 08-01-2009, 04:17 PM
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Bit late I know, but if your running a stock VW engine with a single stock carb then the best way to stop carb icing is to get a late model air filter(the one with the paper element)

It's got all the correct vacuum inlets and has a massive inlet to attach a warm air pipe to, then you just run the pipe down to a convenient exhaust and let it do it's job.
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Old 08-01-2009, 04:27 PM
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Default Problem solved

buy a pair of heated sox, wrap around manifold & secure with cable ties !voila
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Old 08-01-2009, 07:26 PM
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Quote:
Originally Posted by nutbag1 View Post
buy a pair of heated sox, wrap around manifold & secure with cable ties !voila
HEATED SOX !!!!!! If this isnt a wind up !!!!! where can I get some ????
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  #18  
Old 09-01-2009, 12:41 AM
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Default heated clothing

Quote:
Originally Posted by CUILLINS COWBOY View Post
HEATED SOX !!!!!! If this isnt a wind up !!!!! where can I get some ????
Google it !
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  #19  
Old 27-08-2014, 03:46 PM
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coming into this wiay late.
My VW Trike is suffering this same problem, it caught me out a bit coz when i first got it, it ran quite well then all of a sudden it was spittin and farting about.
Eventually worked it out, i fitted electronic ignition and set the timing up. On the original point i noticed that the point gap was very small, this retards the ignition.
Anyway getting back to the icing problem, i am going to fit some 75mm flex ducting to the exhaust header and hove it strapped to the air filter on the Webber carb.
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