Ashley James Posted September 9, 2012 Report Share Posted September 9, 2012 Tony, sorry I thought you were referring to TR4 carbs. The 4a ones do indeed have springs going down to the central plate. But if you have any leaks around the spindles where they exit from the bodies then as they warm up this will allow more air in which will up the tickover. Try spraying a bit of carb cleaner on the exit points of each spindle while the engine is ticking over, if the tickover increases then you need them re-bushing (Keep the carb cleaner away from the exhaust ) You could try oiling the plastic bush where the throttle pedal shaft goes through the bulkhead and check that the bellcrank locating bolt is correctly assembled and well greased, that also goes for the main and secondary link ball ends especially if they are of the type where you can adjust the pressure of the spring pad (The ones that have a split pin across the end screw.) Stuart. Stuart is spot on and another symptom is having the jets lower than the 40 thou down they would have been originally. Wear on the butterfly spindles and in the holes lets more air through and you have to drop the jets slightly to compensate. Quote Link to post Share on other sites
sandandlime Posted September 9, 2012 Author Report Share Posted September 9, 2012 Stuart is spot on and another symptom is having the jets lower than the 40 thou down they would have been originally. Wear on the butterfly spindles and in the holes lets more air through and you have to drop the jets slightly to compensate. Well, as I said in my earlier thread the jets are most definitely lower than 40 thou. My tickover is also normally around 900/950, as suggested by TR4Tony who was responsible for her 'mild modifications'. As far as I'm aware, he never measured the jet height but had her set-up for max power on a rolling road, so I don't have a sensible benchmark figure to start from. Unlike Tony, I'm not looking for max power at 4500 - 5500 so the lower end of the range is more critical to me. I have sprayed a couple of volatile aerosols onto the spindles but haven't observed any noticeable change, although I can't say that I've ever achieved a particularly steady idle speed. On the basis of ruling things in or out, I will repeat the process again next week just to be certain. Given that I'm committed to a rally of around 350 km next Sunday,I might just have to live with this 'feature' for a bit longer than I'd like. Thanks again, Tony Quote Link to post Share on other sites
Alec Pringle Posted September 9, 2012 Report Share Posted September 9, 2012 Hi Tony, if the good Mr Scheach built the car for top end maxpower, then he'll have made at least a half reasonable job of just that. A bit of twiddling and tweaking isn't going to shift the priorities down the rev band, nor turn a bit of a banshee into a basenji. At the very least a proper session on the rollers, or is it more a case of milder cam and reduced cr ? If you're doing a 350km rally next Sunday, then surely max power at 4.5-5.5K is exactly what you need . . . . or am I missing something ? Cheers, Alec Quote Link to post Share on other sites
sandandlime Posted September 10, 2012 Author Report Share Posted September 10, 2012 Morning Alec, I totally agree with what your comments and, in general, the way she is set-up is overall pretty good. The rally is more 'touristique' than performance, which is fine for me. The only (and I hesitate to use that word as I know that another gremlin will raise its head at the most in opportune moment) issue is when the idle revs build to 1300 or so and I'm trying to get through a town centre without skittling too many bystanders. We have thougt that the best way to set her up is on a rolling road again but, as far as im aware, there is a bit of a dearth of such things in these parts. Probably even more of a dearth of people who understand the subtleties of SU carbs. But I will keep looking. In the meantime, it's back to ears and screwdrivers! All the best, Tony Quote Link to post Share on other sites
stuart Posted September 10, 2012 Report Share Posted September 10, 2012 Is your throttle assembly like this. You could always do this with the return springs to give them a bit more "pull". Stuart. Quote Link to post Share on other sites
Guest ntc Posted September 10, 2012 Report Share Posted September 10, 2012 The cam or cr should make no difference, you have weak springs or you have air getting in Quote Link to post Share on other sites
stuart Posted September 10, 2012 Report Share Posted September 10, 2012 Check the PCV valve and its associated pipe work and manifold fitting for leaks as well. Stuart. Quote Link to post Share on other sites
sandandlime Posted September 10, 2012 Author Report Share Posted September 10, 2012 The cam or cr should make no difference, you have weak springs or you have air getting in Or even both both, Neil! I'm less sure than I was about air leaks occurng somewhere for no other reason than I'm running out of ideas. I really like your suggestion wrt sprng arrangement Stuart. And yes, what you've shown is exactly what I have. It is, however, the lack of energy in the linkage that seems most perplexing but I'm not sure exactly how lively or otherwise it should be. I'm hoping that I can get back onto Ludo Thursday/Friday; I seem to have become a full-time mechanic at the moment. Four pairs of brake shoes removed from our Alvis today and dispatched for relining. Next on the list is engine/gearbox mounts. Don't you just love being upside down with *r*p dropping in your eyes! I would put this to one side but my wife wants her back on the road in time for the impending arrival of relations frm Australia. Your wish is etc... Thanks to all again. I'll be back! Tony Quote Link to post Share on other sites
Guest ntc Posted September 10, 2012 Report Share Posted September 10, 2012 (edited) Tony Remove idle screws lift pedal, it stop linkage if not air leak, you should also check where the butterflies are sat it could have slipped on the bar note the clamps Edited September 10, 2012 by ntc Quote Link to post Share on other sites
stuart Posted September 10, 2012 Report Share Posted September 10, 2012 If you remove the main underneath throttle bar at the bulkhead end and then try working the bar backwards and forwards. There should be appreciable spring resistance and no sticking anywhere across the range and the throttles should return to rest. The triangular piece on the main underneath bracket is very well known for wear on its spindle and can cause drag on its mounting shoulder. Stuart. Quote Link to post Share on other sites
graeme Posted September 11, 2012 Report Share Posted September 11, 2012 (edited) Tony, I had a similar problem a few months ago, it turned out to be one of the balls in the linkage had become marked somehow and was preventing the linkage from returning to rest. I dressed the ball with a needle file and it is OK now but I will replace it soon. I suspect it is another repro part made of softer material than it should be. Cheers Edited September 11, 2012 by graeme Quote Link to post Share on other sites
sandandlime Posted September 11, 2012 Author Report Share Posted September 11, 2012 Thanks for the suggestions Neil, Stuart, Graeme. That gives me something to get stuck into. I've spent most tie just exploring fr air leaks but without finding anything definitive either way. All I need to do now is to shrink my hands (maybe remove an excess of fingers?) so that I can access all these places! Attachment of the bulkhead spring seems better suited to someone with an exta joint in their wrist. Tony Quote Link to post Share on other sites
sandandlime Posted September 19, 2012 Author Report Share Posted September 19, 2012 (edited) Just to close this thread, I am pleased to say that I think that I might have finally got her sorted. I was a bit preoccupied last week and didn't get chance to adjust anything until Friday afternoon. At this time, and after an early trip around the Angoulême circuit before it was fully closed off, it was apparent that the building of revs was still an issue. By 8:00 pm I still hadn't got anywhere but decided to finish for the day as I was beginning to lose it. Saturday, after a few adjustments and a short test drive showing mild improvement I had an idea. Three adjustments seem to have finally got me on the right track: The long throttle linkage was adjusted to provide greater length and more elongation on the bulkhead return spring The timing was retarded a couple of degrees The jets were set back to 40 thou below the bridge, as suggested many times by Ash and others. After our 350 km run on Sunday, involving quite a lot of low speed, low gear work and a couple of blasts along the motorway at 80 mph I can report that she performed admirably. An inspection of the plugs on our return suggested that all in all things are pretty much as they should be. Thanks to all again for all the pointers and generally useful advice. Tony I forgot. There was one more thing I did which was to invert the diaphragm on the PCV. I'm not sure which way up it should be. The WSM shows a dished cap and the diaphragm shaped to fit. Mine has a flat cover plate, so should the diaphragm be dish up or down? Edited September 19, 2012 by sandandlime Quote Link to post Share on other sites
stuart Posted September 19, 2012 Report Share Posted September 19, 2012 AFIK it should be dished down to sit in the body of the PCV. Stuart. Quote Link to post Share on other sites
sandandlime Posted September 19, 2012 Author Report Share Posted September 19, 2012 AFIK it should be dished down to sit in the body of the PCV. Well that's the way that it is now. To my, admittedly not very good eyes, the WSM shows it the other way up with a dished cap. I tried to think what would happen to the diaphragm as it became pressurised but failed to sort it out when my brain became too full of cotton wool. Either way, it's better now so I'll probably leave it as it is. Tony Quote Link to post Share on other sites
littlejim Posted September 20, 2012 Report Share Posted September 20, 2012 Just to close this thread, I am pleased to say that I think that I might have finally got her sorted. The timing was retarded a couple of degrees Thanks to all again for all the pointers and generally useful advice. Tony Mine idles way too fast if I don't get the timing spot on. Quote Link to post Share on other sites
silverfox4 Posted October 25, 2012 Report Share Posted October 25, 2012 I found this thread very useful in assessing a similar problem and have since re-bushed the front carb which was the culprit. I think my present question is best accommodated by adding to this thread - hope that is OK. Ques: Can anyone advise what the "correct" length would be for the lower/main link from the throttle pedal arm to the the bell crank. The question posed in thread #25 regarding this length was never answered. Mine is 228 mm which seems too long as th top surface of the bell crank is no level (upward slope) which appears to stress the vertical secondary link and throttle sgaft assembly a little in that it has a side force first before pulling dpwn. It looks like the arc movement is causing this. Also where you set pedal arm also dicates the link length The pictures posted by Stuart represent my set up as well. Anyone got a bal-to-ball measurement for the main link?? Thanks and cheers Alf Quote Link to post Share on other sites
peejay4A Posted October 25, 2012 Report Share Posted October 25, 2012 Hi Alf. This looks like the question I asked in this thread: http://www.tr-register.co.uk/forums/index.php?showtopic=37564&hl= Quote Link to post Share on other sites
silverfox4 Posted October 25, 2012 Report Share Posted October 25, 2012 Hi Pete, yes it is, hence my thought to re-open the question on your thread - hope that is OK? I too am looking for a reference length to see if my linkage geometry is close or way off Quote Link to post Share on other sites
silverfox4 Posted October 25, 2012 Report Share Posted October 25, 2012 By the way Pete, that is one terrific 4A you have - brilliant! Quote Link to post Share on other sites
silverfox4 Posted October 25, 2012 Report Share Posted October 25, 2012 Hi Pete. Sorry I had a senior moment and mixed up the threads on the question regarding link lengths - all sorted. Did you set yours at the 215 mm/8.5" and how did it work if I may ask? I have just tried 8 5/8" but this now needs a longer ssecondary/vertical link for the motion of the bell crank to be fluid, so 8.5" would be a stretch without a new threaded section for the vertical link. What would you advise? what is the suggested length of this vertical link? Cheers for that Quote Link to post Share on other sites
peejay4A Posted October 25, 2012 Report Share Posted October 25, 2012 (edited) Alf, I just popped out to the garage for a measure. At the moment my long rod is 230mm ball to ball and the vertical is 90 mm ball to ball. I might have to vary them to make sure that the pedal height is right and at I can get full throttle. PS. I'll be in Ontario in December. Ottawa to be precise. Edited October 25, 2012 by peejay4A Quote Link to post Share on other sites
silverfox4 Posted October 26, 2012 Report Share Posted October 26, 2012 Thanks for that Pete. So the link is probably somewhere between 215 mm and 230 mm. I am now at 220 mm and 78 mm on the vertical which is no good. I think vertical link now needs to be longer, but at this point, I am essentially at the limit of the travel in the ball ends - only 6 mm captured at each end. (I don't know how to post images yet so can't help with thew clarity that might bring) I will get a piece of threaded rod and make a longer vertical link closer to the 90 mm length and then increase the long length to around 225 mm. I feel the objective must be to get the top of the bell crank parallel to the long link, as that may give a better motion to the vertical link namely more straight-up-and-down, and less side force on the carb throttle shaft. My Son lives in Ottawa (Orleans side) so we go quite often to visit, though it is 500 kms and a 4 1/2 hour drive from Oakville. Actually they used the TR4A for their wedding in the Gatineaus. Are you on business or visiting? Many thanks for your help here Quote Link to post Share on other sites
peejay4A Posted October 26, 2012 Report Share Posted October 26, 2012 Alf. Be careful that you get full throttle opening. I'm still very early in getting mine set up but the ball joint on the throttle plate shaft needs to be above the centre line of the shaft to get full opening. Quote Link to post Share on other sites
silverfox4 Posted October 26, 2012 Report Share Posted October 26, 2012 Pete, thanks for heads up. I now have the whole linkage off, so can get some better measurements and start again. Quote Link to post Share on other sites
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