Manky Monkey Motors

After riding my trike last weekend i found it died on hills it seems over geared if i drop a tyre and rim size from 14" to 13" would this help O but iv also found that this model bike a yamaha fj1100 suffers with loss of second gear so not helpfull it will sit all day at 3500 revs producing a 70mph with 7000 revs in reserve if you look at Andy's photo of the trike i bought it sits slightly high in the rear dropping a size at the rear would bring the back end down and maybe aid its performance any ideas would be welcome THANKS in advance

just bringing this back up any help out there

I'd say yes Alan, but I'm certainly not the most techy minded one here -I tend to work on the Try It & See priciple, rather than calculating things beforehand. Smaller wheels/tyres should give you faster acceleration, so probably better pulling power as well. You seem to have plenty of revs there to play with & don't mention it revving itself to death at the moment, so I'd go for the smaller size. Any chance of finding a cheap old set of steel rims in a scrapyard, just to try, before you spend out on new wheels & rubber?

thanks Andy will try some 13's

you couls even try 12,s  ,,late model old shape mini,,  may even be a couple of steels up the yard (i used to build and race ministox)  will look tommorrow if i get chance

Before you take expensive measures,such as changing wheel sizes etc. are you sure that the motor performs as it should do? What do you mean by "this model loses 2nd gear?",frankly with all that engine capacity working to design it should have no probs. pulling the gearing developed by 14" wheels. How steep were the hills, 1:3, 1:4, or what, and what gears could you pull, there's a deal of info required here before a reasonable course of action could be advised!finally, check your final drive ration from the gearbox, and do a calc. against the diff. ratio,then compare it with the orig. bikes final gear ratios, just to have an idea of what's what, Morrag

thanks for info the second gear jumps out as you accelarate and its a known prob with this bike didn't know when i bought it as i trailored it home it was only made for one year 1985 then it was replaced by the fj1200 and the second gear was then sorted.the hill was a bout 1.-3. in the dales if i had second it would have gone up no prob that is why im going to look into a smaller back wheel other wise total engine strip to replace second gear thanks for all your answers

Well, I would sort what you have first, and with all those "cc's" in hand, if you still need 2nd gear to get up a climb like that, I feel you have other probs. Check out your overall gear ratios now as against the orig. bike, first!otherwise your navigating by guess! The 2nd gear prob. is the first repair I would put in hand, anyway,as I feel a reduction on rim size as you propose will make little overall difference, but that's conjecture, so do the calcs. first with regard to gearing, and then decide. What rear axle do you use? I wouldn't jump the gun and involve yourself in unnecessary, and possibly pointless expense until all these avenues are explored, Morrag

Just realised that the FJ1100 is chain final drive, I had assumed it was shaft like the FJ900, so whilst all the advice already given still applies,the cure is simpler,as to lower your overall final drive ratio, you only need to drop poss. a tooth or so at the gearbox. I believe the standard sprocket mix was 17/42, or a 2.47:1 ratio, so check what you have at present, then if you feel the need act accordingly, however with 125 bhp available, and being already down on the standard 16" rear wheel size, I would be surprised if its required, sort the 2nd gear problem first! Morrag

you might be able to fix the 2nd gear selector problem through the sump and not have to split the motor. try the fj1100 web site or the xs1100 one. They are all helpful people.