View Full Version : TR2/3/3A need TR3 engine help

07-29-2006, 07:03 AM
My #1&2 cylinders are running way rich. 3&4 are normal. Compression is 155-158lbs. on all four. I've adjusted the carbs, dismantled and cleaned them, centered the jets, set timimg, changed position of ignitor magnet ring, changed plugs, wires,and dist. cap. It runs very rough at idle and I can disconnect the #1 plug wire with no change. I checked to make sure the plugs are all firing. The first two plugs become black and sooty very quickly after cleaning. Do vacum leaks, such as throttle shaft or vacum advance fittings create overly rich or lean conditions on the SU? Any tips? Thanks

07-29-2006, 07:19 AM
Check the jet return spring on the front carb. Make sure it's returning the jet properly after choke is applied. These springs sometimes become stretched and no longer perform their intended function. Check choke linkage/adjustment.

Have you checked for vacuum leaks? Spray a little carb cleaner around the throttle shafts with the engine running and see if you get a change RPM.

You also might try continuing to lean up the front carb a little bit at a time and test drive it after each adjustment. I know I sometimes have difficulty setting the mixture properly using the "lift a piston" method (that's why I bought a Colortune).

Good luck!

07-29-2006, 09:08 AM
I would suspect that the front SU still needs adjustment either in the connecting linkage rod connecting the two carbs, or the mixture adjusting nut, or it is not returning to the full choke off position as previously mentioned. You should probably follow a carb adjustment manuals advice from the beginning to readjust. Yes... throttle shaft wear will make it very hard to adjust carbs properly if air is entering through throttle shaft or vacuum advance. This should tend to cause it to lean out due to more air though not run rich. quick check is to spray non-combustible (very important non combustible) carb cleaner in shaft vicinity and see if change in engine rpm. You mentioned that you replaced distributor wires and plugs. Any chance you put them back on incorrectly. Check fire order in relation to rotor position on distributor. There are some caps out there which fit but are not the same as original and if you are not paying attention the fire order will be wrong. You may not notice any change when you take #1 wire off because it's not sparking when it should be due to wrong hookup of wire, or the plug is so fouled it will not ignite the fuel Just a thought. I would start over with my initial tune up and see where I may have missed something.


Geo Hahn
07-29-2006, 09:32 AM
...Check fire order in relation to rotor position on distributor...

[/ QUOTE ]

And the sequence of the wires... so easy to switch 2 adjacent wires and amazing that the TR runs as well as it does on 2 cylinders. (anticlockwise 1-3-4-2)

07-29-2006, 09:54 AM
Check your mixture needle and spring, see if the shoulder is flush with the slide. Also see what needle it is,it should be SM I believe.Also have you tried running your jet up flush with the carb bridge.Do this first,before my other suggestions,that will make the jet almost shut off. Last but not least ck valve adj, and swap the plugs around to clean the sooty ones up.

07-29-2006, 02:00 PM

Another possibility:

Check the needle valve and float. If the needle valve is leaking or the float is sticking, it can cause overrich condition in one carb.

Could be failed plugs, too... although it's unlikely that two right next to each other would fail at the same time. Easy to check, though, just swap them around.

Keep us posted!


07-30-2006, 09:19 PM
Thanks for all the suggestions. I went through and checked them all. I also checked the leakdown of each cylinder and they are all relatively good at 20%- 25%. Not too bad for an engine that had its last rebuild in 1984. I checked that the jets are fully up and that the needles (both SM) are in their correct positions. I switched the two needles also. I will go tomorrow and purchase one step hotter plugs. I also wonder if the inside of my combustion chamber is thick with soot: would it affect combustion? So here is the list:
New Pertronics- could it be faulty?
New wires, new cap, made sure they were placed correctly
New plugs, watched the all fire
Set timing 4deg. BTDC
Compression test- all were between 155-160lbs.
Leakdown test- all were 20%-25%

I didn't get to crank it up tonight but will try tomorrow. If it is still missing I will put in hotter plugs, maybe mist some water into the carb(I heard that this will "decoke" a combustion chamber). If that fails then I will change carb placement to see if the problem moves with it.
Let you know what happens.

07-31-2006, 10:45 AM
You have a new cap so my thought may be mute. The fact that you can remove one plug wire and it runs the same has me thinking of a problem I once had that was near the same. In my case I started removing plug wires and the first one I took off made it run better. It turned out to be an arc in the cap that was making two plugs fire at the same time. With this 'problem' it seemed that all plugs were firing but two were going twice per every two revolutions instead of once. Look inside the cap very carefully for a carbon trace.

Geo Hahn
07-31-2006, 11:42 AM
... If it is still missing I will put in hotter plugs, maybe mist some water into the carb...

[/ QUOTE ]

What I heard before was that 1&2 were running rich which, as Alan noted could be a needle valve/float stuck open. But I have encountered a miss on 1&2 when the valve was stuck closed. This was on a carb with those pesky Grose Jets (didn't even know it had G-Js until this happened.

Easy to check -- took the cap off the float bowl and it was bone dry.

08-06-2006, 11:06 AM
I followed everyones' advice and some of my own. I went through every tuneup task and made sure everything was set right, re-adjusted the float levels, checked damper oil, needle seating, centering, jet position and #, cleaned spark plugs and reset wires into dist. cap. and then balanced carb intake. Well something worked and now it is running much smoother, tho not quite as smooth as I would like. I'm going to drive it some and check plugs everyday to watch their progress. I did dismantle some H6's to clean them up and substitute them on my engine. I was quite surprized at how much the throttle shafts had worn. I'm going to start a new carb post to get feedback on that. In a couple of weeks I'll report on the fouled cylinder issue. Thanks to everyone.