Scooterotica

Need some advice on timing and the effect it has on performance/heat generated etc. I'm running my 175 iron conversion at 19 degrees and suffered a soft sieze on the way back from Wicksteed at the weekend, it seemed to get rediculously hot as well so I'm thinking would anything be gained by altering the timing at all?

19 degrees is about right for a 175.It seems like you have an air leak somewhere.

If the ignition system is a 12v static system made in India,when it was fitted,was it strobed.If it was timed just using the flywheel marks,it could be a long way out.

HxPaul wrote:19 degrees is about right for a 175.It seems like you have an air leak somewhere.

yes just found the problem, the carb clamp bolt had self stripped itself leaving the carb to flop about "like a cock in a stocking" and therefore drawing to much air in hence the soft sieze. Just honed the barrel and lapped the head/barrel faces, cleaned up the piston and freed off the stuck top ring and it lives! Getting just over 120 psi comp pressure which hopefully will increase a bit once it's bedded in.

Think I'll leave the ignition timing be as its obvious that was just me barking up the wrong tree!

A bit of a ball ache having to strip the top end,but at least you found the problem and rectified it,happy days.

Yes I'm going to dril,out the carb clamp and fix an m8 bolt through it to stop that happening again.

NB: 19 is normally OK for most 'off the shelf' iron 175s but some cheapo ones use the 150 head opened to 62-63mm but no increase in combustion chamber volume, which leaves the compression way too high on normal exhaust duration and will cause the bike to run hot. On these, it is very common to find that 17 is required to keep it cool.