OCD.......obsessive campervan disorder

Monday, May 9, 2011

A discussion on Carb linkage balancing...need to check this

Ensuring the linkage is symmetrical....and I quote:

Ref:

http://www.aircooled.net/gnrlsite/resource/articles/dualcarb.htm

"The procedure I have outlined here all dual carburettors, even dual single bbls (except you only have one mixture screw per side, since one barrel feeds TWO cylinders). Other important things to check are that the linkage pieces "match" from side to side, and from carburettor to carburettor. The linkage has to keep the carburettors at the same adjustment at ALL throttle positions, not just idle! Part of this is that the carburettors have to open at the same rate, and if one side opens faster than the other, the car may run fine at idle, but hesitate and miss when on the road. Make sure the linkage is symmetrical. Also, you need the vertical throttle rods (If it's crossbar linkage) to be matched in their pitch from vertical. This ensures that the two carburettors open at the same rate, since the crossbar is rotating the same on both sides.

Sometimes you have to add/remove washers from various ball-joints on the linkage to adjust the threaded rods so they are at the same angle on both sides of the engine, but the engine will run SO much better, and it's amazing how many "experts" miss this important detail. "

NEED TO CHECK THIS AS MAY BE ONE REASON WHY CARBS ARE OUT OF BALANCED WHEN THROTTLED ON!!!

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Arrghhhh what's happened (update....)

Just spoke to Jim at The Engine Shop explained what we thought the problem was and he said yeah will be lazy on 1 and 3 as running the high lift cam i.e removing leads on 1 amd 3 won't make a difference but when high revs will kick in .... but I said the timing is retarded and point gap is tiny ... he said to go back to basics and fit the og pulley (said it should have tdc mark if og vw pulley wheel not sure it does?) then check the advance he confirmed it should be 7.5 btdc and that I can change the timing if this is not the reading we get and we know what we are doing! ! He also said to check the point gap this should be 14 thousandsth....we can adjust if the gap is not that and won't invalidate warranty!

Should I think the plan is back to basics do a manual check to ensure tdc at 1 and work from there then check with timing gun etc and advance as required to 7.5 ..... going to recheck every gap from stone cold tonight update to follow......

Inshallah

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Arrghhhh what's happened ?

I Can't sleep now the engine is not good : (

Initial problem we had was getting the carbs balanced and getting a good base setting what ever we did the carbs were flooding; wouldn't idle andc no matter what we couldn't achieve good base setting, very strong fuel smell and plugs wet no. 3 and 4 nearside bank of carbs (twin weber ict's 34)

Carb float settings checked 6mm 12mm then found a chunk of swarf in float chamber ? Removed this carbs now running no overrun or flooding. Checked fuel into carbs ok now but still a question over fuel to no. 3 but makes little sense as fuel getting to no. 4 and the plugs look rich (were wet at one point)

Next and BIG problem:
As couldn't get engine to run smooth but having checked the carbs and fuel we then Removed no. 3 lead and there is no change in engine speed so no. 3 is not firing ?

Checked firing order was ok on dizzy and leads fitted correctly tried new spark plugs and checked with known good dizzy cap and leads still no fire on 3!!!!

Thought this could be overtight valve on number 3?

Quick check of engine timing its set at 2 degrees before tdc by TES and clearly wants to stall (shouldn't this be set at least 7 degrees advance?)

Checked the point gap this is very tight almost no gap
Point gap should be 16 / thousandsth ??

This would result in weak spark missed or weak ignition / spark?? I.e. not firing in number 3

checked valve clearance very tight on intake and exhaust 4 and 3 these were very tight almost no gap on 3 and 4 intake but also exhaust. Adjusted to recommended gap as per running in instructions 8 / thousandths

We have read for compression around 120 and within about 5 for each so shows ok compression ? possibly need to recheck compression on number 3 carefully!

WHAT HAVE WE MISSED ?

http://www.vw-resource.com/tune-up.html#timing

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