snowric Posted March 7, 2015 Report Share Posted March 7, 2015 Today, I have had a go at balancing my throttle bodies, did a bad job but got there in the end. Ideally I was trying for the 'all shut' and idle set by the air screw method but I would not get number 1 and number 5 to shut properly even when the airwlow in all other butterflies was very low. i even saw lean backfire from number 5 where i prsume excess airflow is causing weak mixture at idle Gorgive the dumb quesditon but do the butterlies in the same body get bent - ie can they become 'unsynchronised' or is this different wear? is this a diy fix ? can you get new butterflies? I have got good balance now across the three throttle bdoies and it drives nicely and am not getting any lean backfire on number 5. I also see Prestuge rebuilds them... appreciate the advice as ever. Snowy Quote Link to post Share on other sites
AndrewP Posted March 8, 2015 Report Share Posted March 8, 2015 Snowy, Simple answer is yes. The spindle can twist. Before anything, check that the spindle is free to twist and that one end isnt sticky/seized, check that the bushing in the TB isnt excessively worn either as you can get air leaks around here as well (search on the forum..there are a few good posts where people have line bored and bushed the TB' to eliminate this problem). Then..Id be checking that both the butterflies are shutting fully. Loosen the small screws that hold the butterfly in the spindle a bit, then with the linkage removed (so as to allow the butterflies to shut fully), flick/snap the butterflies shut a few times to seat the discs in the intake. On the final time, snap shut and nip the screws back up while the butterfly is fully closed. If you still have a large difference between the pair, then (and if your game) you can hold one side and gently twist the other side with your finger to get them the same. Go careful though! If all else fails, the main suppliers do have new spindles. Expensive mind. Hope it helps Quote Link to post Share on other sites
TriumphV8 Posted March 8, 2015 Report Share Posted March 8, 2015 (edited) That was simply not a good method to balance the manifolds. The critical throttle position is where the plates open a little bit. Not only this is often in use when driving but also differences count more due to the small amount of total air passing the plates at this state. So the sync must be done at the 2000+ rpm achieved by shortening the throttle cable. Many of the part suppliers do not offer proper manifolds and in my opinion even the bushing of the manifolds is solution of yesterday. Weak bearings and connections are the base of bad rumours about PI system. Best way is to use ball bearings with integrated shielding from RC-cars: So first get perfect manifolds with bearings and connectors including the underslung cam. There is also a very weak point with the rubber bearing in the middle. Good systems are split up to employ a needle roller bearing in the middle! Edited March 10, 2015 by TriumphV8 Quote Link to post Share on other sites
grumpy2 Posted March 8, 2015 Report Share Posted March 8, 2015 Hi. I did mine about a month ago. Balanced at 1200 rpm and it's made a massive difference. Happily cruises in 4th at 30 mph now and will pull away cleanly up to 70. Would cough and splutter at 30 before and chug and misfire pulling away. Quote Link to post Share on other sites
snowric Posted March 8, 2015 Author Report Share Posted March 8, 2015 Thanks triumph V8, I rebalanced at 1500 rpm and made a big difference to smoothness but number 5 and 1 flow much much more at tick over hen the other four are practically shut. Can anyone PM me their view on the best refurb service as it is expensive to hve it done badly ! Quote Link to post Share on other sites
TriumphV8 Posted March 8, 2015 Report Share Posted March 8, 2015 The spindles can be twisted by removing the airbox and rubber tubes. Give full throttle by a second person and grab both throttle plates with long nose pliers (Spitzzange?) Than twist the plates carefully against each other and not too much, better several times and get a feeling by that what that force does to the sync than one time too much. Check if a proper sync can be established and if necessary go through the hole process again. As the spindle is slitted and made from brass it can break easily. If that happens do not worry it was spoiled anyway and new ones can be obtained from Rimmer. Best refurbish was done by German Ulli Schaubhuth but I fear he retired. Quote Link to post Share on other sites
stuart Posted March 9, 2015 Report Share Posted March 9, 2015 Can anyone PM me their view on the best refurb service as it is expensive to hve it done badly ! Talk to Neil Ferguson 07977001571 Stuart. Quote Link to post Share on other sites
JohnG Posted March 9, 2015 Report Share Posted March 9, 2015 Definately Neil Really good guy Quote Link to post Share on other sites
snowric Posted March 9, 2015 Author Report Share Posted March 9, 2015 Thank you for the suggestion. Quote Link to post Share on other sites
Grabea Posted March 13, 2015 Report Share Posted March 13, 2015 Thanks triumph V8, I rebalanced at 1500 rpm and made a big difference to smoothness but number 5 and 1 flow much much more at tick over hen the other four are practically shut. Can anyone PM me their view on the best refurb service as it is expensive to hve it done badly ! If I understand the system correctly all the butterflies should be closed at tickover so shouldn't flow any air, the air gets to the engine via the needle screw at the front of the TBs which takes its air from the air box direct, if air is being drawn through 2 of the butterflies but not through the remaining 4 then something is not right. I think I've seen elsewhere that to set the butterflies you slacken off the screws that hold the butterflies to the spindle, hold both butterflies closed and then tighten the screws while holding them shut, worth a try before trying to twist the spindles? Best of luck Graham Quote Link to post Share on other sites
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