my carbs are not happy

[nicolas]

just posting this to know what i need to check tomorrow and this weekend.

my engine is doing some weird stuff lately and i can't seem to fix it. i have added a sump last weekend and set the valves, because i lost compression on cylinder 1 and 3. turned out that the plug on number 3 stripped the tread so i put in a helicone. so that should be ok. i pretuned the carbs as said in the CB manual and bolted everything back again. now i wanted to fire things up and it did run for a while but i couldn't get it steady at idle. it measured 6 on the synchro on all 4 barrels but i couldn't get lower. it ran like that first and i wanted to adjust the mixturescrews and it did not respond much on 3 and 4 (so i am guessing a airleak somewhere) and did react on 1 and 2. so i lowered the rpms again and it just died. i tried to fire it up again and all i got was a big bang out of one of the barrels. and after that i started it again and it ran but went up and down in rpms a lot and i had to hold on to the gaspedal. i thought i had a bad dizzy (still the 019) so i switched to the 010 again and had to set the mark on a totally different point. with the 019 it was on 6 o'clock and with the 010 it was on 4 o4clock if you see what i mean by that. timing was both times set at 10° BTDC
all weird things for me... so i quit and will look things over in the weekend

my gut feeling is telling me something is wrong with the engine, but i don't know what...

[Fasterbrit]

Really would be a good idea to do a leak-down test on all 4 cylinders. That way you will have an accurate idea of piston and valve condition.
When you helicoiled the plug, did you make sure every last bit of aluminium swarf/particles was removed from the plug hole? There is a possibility that you have trapped a small piece of metal between your valves and seats on that cylinder. The piece of metal might get imbedded into the valve seat if you are not lucky. This causes loss of compression.
Hope it goes well for you. Matt

[nicolas]

i thought about it, but i blew the cylinder out while the exhaustvalve was open. so that was ok, but i can't really be sure. i don't like it to have put in the plug with the heads still on, but it is done like that many times, so did it as well. but nethertheless the initial stumbeling and hesitation and general hickups of the engine didn't stop after i did it.
just how do i do a leakdown test?

[Jim Ratto]

what type of carburetors?

[Rasser]

I know it sounds simple - but did you check if you had one or two plugged idle jets (that could explain why adjusting mixture screws didn´t work)?

did you try pulling the spark wires one by one to narrow down the search ?

[Felix/DFL]

just how do i do a leakdown test?

Do yourself a fever and buy a Compression tester.Even the very cheap one`s work ok.Then you could see if everthing is OK on the mechanic side and leave this nasty thought behind you.
Before that I would check if the 1st cylinder is really in BTDC when the distrubuter is at the 1st mark.
Pulling the spark wires is an all time good idea

Greetz

[nicolas]

carbs are 40IDF's
and i will take a look at the idlescrews and plugs and see if anything is caught in there.
and yes i have thought about a CR meter and i got ahold of one last week and that is how i found out the valves on cylinder 1 and 3 were not closing of fully. but you can NOT reach the plugs on a type3 with IDF's. it is even very hard to put on the wires on them. there is no tool that i know of that can take out a plug without removing the hole carburator... but i guess i have to do that agian this weekend as it is not responding very well. otherwise what am i looking at if the carb is backfiring through the intake (like very loud bangs) me notte like