Good day Billy…

Q: Perhaps you can help? I have a Yamaha MT-09, nice to ride but every time I ride around town, between the 1500 to 3000rpm range, the bike tends to ‘surge’.

The sound from the exhaust doesn’t change but there’s a noticeable change in speed, as if something is grabbing and releasing. I’ve had the throttle bodies synchronized, but still with no change. I’m now thinking of mapping the ECU – any advice?

Phillippus Opperman.

A: Before you go up that expensive path there is one thing you can check that riders tend to forget. Buy a decent fuel-injector cleaner and put it in to the petrol tank, these can sometimes remove deposits from the injectors that could cause your irritating problem.

Does the bike still have, or did, the ‘power-valve’ installed. If set incorrectly that could also have this affect?

Try these recommendations first and let us know if it makes a difference?

BillysBikes.co.za

Q: Hi guys and thanks for a superb site, we go onto it everyday, so keep it going.

I’d just like to ask a question. I read about ‘straight cut’ gears and/or ‘helical cut’ gears and was wondering if you could clarify the difference, and the advantages, if any?

It was just something that popped up in our local pub conversations – looking forward to the answer.

A: Both are usualy used in the primary drive from the crankshaft to the clutch/gearbox. Quite simply the helical gear system is to make the mechanical engine noise, not so noisy, and that’s about it. However if you put a lot of extra power though a helical drive (turbo charging for example), it can ‘deflect’ the gears between the crank and clutch, as they can push/ride apart, causing irreparable damage.

Straight cut gears do make more mechanical noise but offer a stronger direct connection between the crank, clutch and gearbox – drag racers especially choose this due to the shock loading off the line. If fact all modern super bikes have primary straight cut gears now because of the high horsepower output.

If you look into a car gearbox they’re usually helical cut – again to keep the mechanical noise to minimum.

Q: Hi guys. I’ve just written this message late at night because I’m really getting annoyed and, asking for help.

I’ve just bought a used Big Boy pit bike (125cc), that didn’t run when I bought it. I’ve replaced the spark plug, installed a new air-filter and changed the engine oil. The plug does have a ‘spark’ when I kick over the engine, so it’s not that. I’ve also taken off the carb and cleaned it to perfection as the jets were blocked with old, and sticky, petrol.

But it still won’t start and the engine seems to have good compression. Have you any ideas what I could look for next?

Kyle.

A: Yes we can advise and it’s an easy thing to check. Take off the two small valve covers on top of the engine and check the tappets for free play. They’re easy to adjust and you only need a 9mm spanner and pliers to hold the top of tappet.

You’ll need to find ‘feeler-gauges’ as well and set the clearance to 0.15mm between the tappet and the top of the valve stem. Once set turn the engine over a full cycle and check again.

This is a common fault if those bikes don’t start. So that should take away your anxiety.

Good day Bill,

Thank you for the entertaining and informative review on the Gixxer 150! Love it! I had my eye on this bike for a while as a first bike for my wife. Your review came in the nick of time and I took the plunge.

In your review of the bike, you noted the possibility of tweaking the carb jetting, and also getting clever with the gearing. Could you possibly direct me to someone capable and knowledgeable who’d be able to assist me with such options without messing up the bike? I’m certainly not an expert on this, but I do know you don’t want anyone just fiddling with these aspects of your brand new bike.

I appreciate your feedback! Keep up the good work!

Regards,

Anton Potgieter

Hi there, and thanks for the kind mail - hope you 'both' enjoy the 150 as much as we did.

If you live in Gauteng give our Dyno specialists a call, he'll know what to do? His name in Noddy (084 430 9090). 

Have fun...

  Bill Hunter