jack_the_lad Posted January 17, 2011 Report Share Posted January 17, 2011 Is it a recent 230 build? Not wanting to "name names" incase this suggestion is wrong, however, I have heard that some "non-Serco" alloy barrels can "ovalise" due to the position of the pushrod cut-out. Just wondering if it might be this, exacerbated when the engine runs hotter, thus losing compression? Just a wild thought! Just to put your mind at rest the castings for the barrels come from the same supply as sercos and are machined by the same person. Have just seen a barrel that was retuned for said reason on inspection the bore was found to be round and the cause of the persons wear problems are more than lightly glass beads that have not been cleaned of the engine. This problem crops up alot. Quote Link to comment Share on other sites More sharing options...
jack_the_lad Posted January 17, 2011 Report Share Posted January 17, 2011 I have a 230cc Tiger Cub motor with a Dellorto carb, Armac exhaust and PVL style (UPB) ignition. The slow running and mid range power is okay but on long climbs where it requires high revs it misfires very badly and often does not make it up the hill. I have spent the best part of a year trying to get the motor to run correctly but I am getting nowhere and going around in circles. I have asked many fellow Cub owners for help but it mystifies us all. I have checked and double checked the ignition timing which is spot on. I have tried all sorts of spark plugs, main jets, needles and pilot jets but still the problem persists. Currently I have a 35 pilot, 105 main jet and a D23 needle set in the third groove from the top. Mixture screw is 2.5 turns out. Can anybody help? Thanks Jim Try a 42 pilot jet PS if you check the swept volume of you engine you will find is 226cc on a standard 67 mm piston. have you tried it with a different filter? Quote Link to comment Share on other sites More sharing options...
stickinthemud Posted January 20, 2011 Report Share Posted January 20, 2011 ...... It might be that I need more clearance in tappets. Currently 2 and 3 thou. Sounds a bit tight. What cam are you using? 10 thou is recommended for the standard cam and 2 and 4 thou for the R cam. Run my standard cam on 8 thou each. Standard 199cc on Boyer Bransden - Keihin carb. Revs out a dream up to valve bounce without misfiring. Quote Link to comment Share on other sites More sharing options...
jimmydee Posted January 23, 2011 Author Report Share Posted January 23, 2011 Sounds a bit tight. What cam are you using? 10 thou is recommended for the standard cam and 2 and 4 thou for the R cam. Run my standard cam on 8 thou each. Standard 199cc on Boyer Bransden - Keihin carb. Revs out a dream up to valve bounce without misfiring. Quote Link to comment Share on other sites More sharing options...
jimmydee Posted January 23, 2011 Author Report Share Posted January 23, 2011 Thanks. It has an R cam so I think I'll try 2 and 4 thou. I've had a phone call from a guy who read the forum thread and he said I should go back to a standard D40 needle instead of the D23 which I was (mistakenly as it turns out) advised to use. I've also gone down to a 100 main jet. The motor is now revving with no misfire. So hopefully I can concentrate on riding. Quote Link to comment Share on other sites More sharing options...
jimtodd Posted April 1, 2013 Report Share Posted April 1, 2013 Hi there is the vent in the fuel tank big eneough to let air in at the rate the fuel is going out (or preferably biger ) Quote Link to comment Share on other sites More sharing options...
armac Posted April 2, 2013 Report Share Posted April 2, 2013 Hi Jimmy, Duncan here, Just picked up this thread. Your valve clearances sound very tight, have you got the correct clearances for your camshaft as they are different for the "R" cam & the road cam. I have tried tightening down the clearances to make the engine run a bit sweeter, but experienced a similar result to your problem. Also worth checking your push rod lengths, these do wear at the cam follower end then don't open the valves fully. I have gone over to steel ones. the original cub valve springs are incredibly variable, I no longer use them, instead I use springs from a speedway motor. I have also known cams to have been mis-machined so that the cam gear is in the wrong place so the cam timing is out. Judy's bike had a problem in that the valve spring pocket in the head had been badly machined so that it penetrated through to the inlet passage, I imagine that this could happen on either port. However as your engine seems to run sweetly at the bottom my guess is that it is electrics. The only way to sort that is borrow a set & then try one thing at a time, starting with the coil, oh check that the air gap around the rotor is correct, & that the main bearing on that side is in good condition. If it's worn then the crank bouncing up & down will bugger the air gap. the golden rule is only change one thing at a time so you can be sure it's illuminated. Hope you don't get to the stage where the one thing is the bike! see you at the 2-day. Cheers, Duncan. Quote Link to comment Share on other sites More sharing options...
trialsoldtimer Posted April 2, 2013 Report Share Posted April 2, 2013 I gather you have now sorted the problem but as a matter of interest, try running without the filter to see if there is further improvement. I ran my cub with the 1/2 moon type filter and it was too restrictive (the stub dia.on the outlet was too small).It revved out fully without a filter and also with a K&N fitted. Quote Link to comment Share on other sites More sharing options...
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