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Post by tango135 on May 18, 2012 7:32:35 GMT
Sorry to butt in but ive had the same problems with a zirri 4th, i must have stripped the gearbox 7 times and every time used a new gear selector and reshimmed it to death. Same thing jumps out of third. Everything else seems bang on and i know its shimmed right. i am going to strip it again and dump the zirri idea and go standard gearing.
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Post by tony on May 18, 2012 11:06:39 GMT
If its jumping out of third why do you think the zirri is to blame? have a good look at the bosses on the 3rd gear. I bet they are rounded. Or better still stick some pictures up. Are you using a genuine selector? There were a bad batch of pattern ones going about that were machined wrong.
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Post by tango135 on May 18, 2012 11:28:29 GMT
ive tried 3 different gearboxes with same results and changed the gear selector every strip down i would hope that there would have been a good one out of seven. to be honest the selectors didn't look to bad but changed them just in case and reused them in standard engines and they work fine, this is why i can only presume its the zirri xmas tree.
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Post by tony on May 18, 2012 18:07:50 GMT
Mmn... A few years ago before building the falc with a zirri tree and 4th I sat down with charley and precisely measured all the available selectors. Every important dimension. We also looked at the pattern versus genuine lay shafts. The pattern selector was miles off. In places .5 mm out. That's way out of tolerance on something that has to be so precise. We checked drt,zirri,RMS. The drt one has since been improved. The zirri was spot on and looks like a rehardened genuine one. I built the zirri box with genuine selector and raced it for 18 months. It never jumped once. If you want I will look at the box for you next time you strip it and see what's happening in there because a tree won't cause a 3rd gear jump unless there is something seriously amiss. Did you use pk gears with your build?
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Post by spiderwebb on May 19, 2012 0:19:07 GMT
could the two shifting cables be too tight = causing a shift due to tension...??
I always like a 1-2 mm of play with the headset shifting tube
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Post by eean on May 19, 2012 9:28:07 GMT
I dont really know to be honest and I have tried exactly what you are saying here, slackened them off, tightened them, slackened one off a bit, then the other, retightened them fuck knows but am thinking along the lines of stripping it and measuring the gap between the DRT 4th and 3rd standard gear and the same gap between the standard gears if theres not something really obvious like the gear is rounded where the lugs of the selector go or something I know something though, its not getting done soon
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Post by jacques on May 19, 2012 20:22:50 GMT
Use pk if you can.. much smoother action. But you will have to redrill the wheel to fit if you have the early pivot type at the moment. Ta Tony. I've got the standard one...I've managed to improve things a little by tweaking the cable tension, it's not PK style smooth but it's much better.
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Post by Jimmy D on Sept 13, 2020 10:44:49 GMT
Eean.... I know this was 8 years ago (time flies) but did you work out a fix? I'm in the same boat.
So much so that if I twist the gear selector even slightly while in 3rd (even just from a bumpy road etc), it'll drop out of gear.
It was fine prior to installing a DRT Runner. The gears are the right way round and shimmed properly.
The cruciform is new/Piaggio. Cables are tight.
Any thoughts?
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Post by jonnysnatchsniffer on Apr 1, 2021 21:47:15 GMT
when you shim the box dont forget the bottom shim, when you build the box make sure theres a fals neutral between all gears, also when you select a gear when making the box up make sure the lugs are fully flush with the gear indents, it may be you need to lower or raise the lot using a different shim on the bottom to make the lugs and indents flush, tho ive always found the original 1mm shim to fit my needs
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