Fizzy Posted September 6, 2009 Share Posted September 6, 2009 ive just had to abort a trip to a local show because half way there i dared to turn my engine off at a services, and it wouldnt start again. after much fiddling and getting covered in petrol, turns out if i screw the dashpot on properly, the piston sticks. if i undo the screws holding the dashpot on, it frees the piston.the only noticbale thing ive done differently since yesterday when it was running fine is brim the tank with fuel. its rarely full that much, and pulled some rust though the pipes, i replaced the filter, and got mroe orange petrol, but it was running freely through the system, and the float bowls were full of petrol, so i dont think that was part of the problem, as annoying in itself as it is.any ideas ? Link to comment Share on other sites More sharing options...
ferny Posted September 6, 2009 Share Posted September 6, 2009 The pistons are meant to be matched to the dashpots. When you've played with them before you may have swapped them over buy mistake. But if they were working before then there's no reason for them to not be working now.Loosen the screws, wiggle the piston and keep moving it up and down and slowly nip up the screws. It'll be fiddly but eventually you'll find a combination which allows it all to move properly. If you can't then try turning the dashpot 180 degrees of even swapping the two over. Link to comment Share on other sites More sharing options...
piman Posted September 6, 2009 Share Posted September 6, 2009 Hello Fizzy, were you giving it a bit more stick than usual, it could be that the piston had lifted higher than usual. Which points to the piston\dashpot requiring an internal clean. Use a solvent cleaner, thinners or carburettor cleaner, not polish or abrasive cleaner.The other thing is the jet centreing but if you haven't disturbed anything, it would be odd if that is the problem?Alec Link to comment Share on other sites More sharing options...
Fizzy Posted September 6, 2009 Author Share Posted September 6, 2009 99% of my driving is around town, whereas i had covered probably 20 miles of dual carriageway at 60-70 in 4th gear (no overdrive) when i pulled into the services. i rarely do this sort of driving. Link to comment Share on other sites More sharing options...
Fizzy Posted September 6, 2009 Author Share Posted September 6, 2009 well, i dont know what caused it considering it hasnt been a problem in 6 months of driving, but after playing musical dashpots and pistons with 2 pairs of carbs, ive got 2 perfectly working carbs on my car - at least as far as the pistons are concerned.anybody know what sort of needles should in a early mkIV engine ? turns out i had 'M' needles in, but after stripping down my spare carbs, the needles in those looked in better nick, but they were 'BO' ones, and ive put them in. Link to comment Share on other sites More sharing options...
ferny Posted September 6, 2009 Share Posted September 6, 2009 This is from the Haynes which covers all the Spits.Mk1, 2 & 3 - Twin HS2 MkIV - Twin HS2E 1500 - Twin HS4Mk1 - dunnoMk2 - ANMk3 - BOMk4 - AN or AAN1500 - ABTHS2E had the springy bit on the needle?My guess would be that you're meant to have AN. Link to comment Share on other sites More sharing options...
Fizzy Posted September 6, 2009 Author Share Posted September 6, 2009 right cheers. pretty sure my carbs are actually from a mk3 if the manifold and throttle linkage is anything to go by, but they are on a mk4 engine. forgot to mention that so i suppose the BO ones are correct, but seen as i told you i had a mk4 engine, i see your point ferny ;) my bad.nice one. Link to comment Share on other sites More sharing options...
rhodes Posted September 7, 2009 Share Posted September 7, 2009 M needles are for a 1275cc Mini Cooper S Link to comment Share on other sites More sharing options...
sparky_spit Posted September 7, 2009 Share Posted September 7, 2009 rhodes wrote:M needles are for a 1275cc Mini Cooper SSlight thread hijack here.... but talking of Cooper S's, you are not the Mr Rhodes are you? Link to comment Share on other sites More sharing options...
rhodes Posted September 7, 2009 Share Posted September 7, 2009 er no, but I wish I had a pound for every time I have been asked. Link to comment Share on other sites More sharing options...
ferny Posted September 8, 2009 Share Posted September 8, 2009 yamaha_fizzy wrote:right cheers. pretty sure my carbs are actually from a mk3 if the manifold and throttle linkage is anything to go by, but they are on a mk4 engine. forgot to mention that so i suppose the BO ones are correct, but seen as i told you i had a mk4 engine, i see your point ferny ;) my bad.nice one.Not sure if you're saying they're correct because of the carbs you've got. You match the needle to the engine, so BO wouldn't be correct for you. Link to comment Share on other sites More sharing options...
Fizzy Posted September 8, 2009 Author Share Posted September 8, 2009 oh i see.erm.in that case, how much of a difference does it make ? Link to comment Share on other sites More sharing options...
ferny Posted September 8, 2009 Share Posted September 8, 2009 http://www.mintylamb.co.uk/suneedle/Compare them on that. But keep in mind that the scale on that is relevant to the needle, not RPM on the car.AN is richer all over than BO. AAN is similar to BO but is slightly richer at one point. So even if you think you're running too rich with BO it may be down to you trying to compensate for the incorrect profile of the needle. It can make a big difference, but not always. And sometimes you have to fiddle with different needles if your car isn't 100% standard.I can e-mail you a PDF book on SU carbs if you'd like. PM me your address if you want it. Link to comment Share on other sites More sharing options...
.thumb.jpeg.b15b81ef10abeea1c3039ae03c4a9f3a.jpeg)
Recommended Posts
Archived
This topic is now archived and is closed to further replies.