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Bike back together this afternoon {half hour practising in the garden - understanding neighbours!)and it's transformed. Suspect the barrel made the biggest difference but exhaust note is now mellow, motor is so much more responsive off the bottom end and is stronger at top. While the barrel was away I lowered the footrests as low as is practical and this has been a positive step also. Didn't move back, just down. I'd appreciate any info on fork mods and feedback on Hagon or Ohlins shocks. Has anyone replaced the standard rear shock spring with an Ohlins? If so, which one? Cheers.

It's a shame I won't be able to give a definitive answer as to what difference the exhaust re-pack makes - two changes at once, what with the barrel also. Being a test engineer, I should know better! Repacking the middle box on my Bultaco 199 made a sizeable difference and it was nowhere near as choked as the Yam, so I'm hoping for similar. I aim to ride a few trials to see how it pans out before taking a bit off the ignition flywheel. a spare one would be handy though - just in case.......

£100 + vat and postage, which I thought was pretty good considering you're paying for not only the physical work but the knowledge of what to do. He went into a fair bit of detail over the phone regarding other improvement mods. Wouldn't give all his secrets away though which is why I got him to do the porting. This is my third mono - recently bought from ebay but the previous two had the benefit of tuning. The first was in 1985, an "S" version that Simon Wigg used in order to keep fit when he was riding Long Track and speedway. Julian had tweaked it and it went well. We never had the motor apart so I don't know what the extent of the porting was. The second was a new Pinky which we took out to 264 or thereabouts with a std IT 250 piston. The inlet tract was shortened and the reeds were altered and the porting was copied from a Shirty barrel but we didn't lighten the flywheel. Too much for me nowadays tho!!!

Just did my middle box at the weekend. 28 years of gunge, some of which had hardened like glass. Judging by the state of the insides it would almost certainly be worth doing on any old mono Yam. Yet to try it though, just got barrel back from Nigel Birkett after porting, so need to refit that first.

Looking very good! What front wheel are you using?

I have both. The middle box type that I have makes the motor feel "smoother" regarding throttle response but whether the difference is worth the cost is open to question as always.

Absolutely brilliant read! Thoroughly recommend spending an hour or so reading it.

Back in the day I had a 199A, the frame of which completely broke just above the front engine mount. I didn't realise at the time (lack of maintenance) that the head steady had completely broken and had been for some time, which allowed everything to flex more than it should have, resulting in a complete break! I replaced the standard broken frame with one of the last High boy frames with the cut off top loop. As I recall, the back end seemed to work better than the standard frame but may not have steered quite so well. In recent years I had a 199, again with a Highboy but with the full top loop. The rear end didn't seem to work as well as I remembered the first one did but it steered pretty well. Does anyone know if the geometry had changed or is my memory not reliable?

Chances are that they were not 199's, so therefore wouldn't tend to suffer so much from the "gasping" off low revs,if given a handful of throttle.

Interesting reading. With reference to Charlie's post, hopefully Burlen have sorted any issues, however until an independent body confirms that they have, I'm lacking the confidence to buy one. Maybe it's a bit too soon for any feedback.

It's not currently listed in their carburetter settings and spare parts booklet but is apparently supplied with a number 3 slide, 100 main, 106 needle and premier pilot jets and is not mentioned as being specific to a Cub.

Has anyone used the new 20mm Amal on a standard capacity Tiger Cub motor? How does it perform, particularly on a "snap" throttle opening off low revs? Is it as good as the cheap "pit bike" Mikuni type carbs? Comments appreciated. Cheers.

Have to agree with both trialsrfun and wallo! It's not just about riding the thing. It's the tinkering, developing, wondering what to do next, trying different things that sometimes improve performance and sometimes don't and yes it can be expensive! That's why I try to make as many bits and pieces as I can. As for pictures, I'll take and post some shortly. Incidentally, there is a nearly full page pic of my dad riding it when it still had all the steel bits in a Classic Bike magazine of I think 1982 vintage. I seem to remember the front cover featured John Surtees' Vincent Grey Flash.

Ah well, at least my "mostly cub" is tax and mot exempt!.........

Yes, you're probably right! Still nobody letting on as to what they've done to theirs though!