Q: I can’t believe it! I’ve just had my crankshaft rebuilt because of a knackered big end on my Suzuki RMZ 250. A local mechanic/engineer did it, as he said he could, and now I’ve rebuilt the bike it vibrates like a mad thing.

Why could it possibly do this when everything inside the engine is totally new and cost next to a fortune to repair? I just hope I don’t have to take the engine to pieces again and that’s why I thought I’d run it by you first because you seem to have experience on just about everything mechanical in the motorbike world.

Colin Milton     Cape Town

A: I’m sorry, but I do have some bad news for you. You WILL have to take the engine to pieces again and take out the crankshaft. If, as you say, everything is new it can only be one thing. The crankshaft hasn’t been correctly aligned after it was rebuilt. It has to be done correctly by an expert using dial gauges or similar to Suzuki’s critical specifications. If not, it will vibrate like a mad thing and eventually the engine self-destruct, possibly causing irreparable damage to the crankcases as well. You’ll then need a complete new engine!

If you have any problems finding the right people for the job send the crankshaft up to us and we can get it done, correctly, for you.

Q: I purchased a 2005 Kawasaki ZX-12R about 18 months ago, from my local Kawasaki dealer. The bike is in mint condition and goes like a bat out of hell. However, it has a slight up and down idling tendency, when the engine is warm. I’ve been told that these models do that, but I’m not convinced.

Years ago I had a Suzuki Katana 1100, which did the same thing, but it did have a hot camshaft fitted and had carbs, so that could explain that particular bike’s behaviour. I have no evidence of an after market camshaft inside my ZX-12R, but with these new fuel injected engines will it be as noticeable?

Another issue is the fuel consumption because I only get 170-180km on a tank, when the bike is pushed hard. I’ve had the bike on two dynos and it recorded 181hp and 182.5hp, so the engine must be OK internally.

Another question for you is, when I bought the bike it had a 190-section tyre and I recently changed it to a 200 (on the dealers advice), but after 5,000km I began to experience that the bike was harder to turn into a corner, is this normal?

The next problem is more worrying. With 26,500km on the clock the bike has clutch slip when opening the throttle in sixth gear at around 8,500rpm. Will this mean I’ll have to replace the whole clutch or just the friction plates?

Thanks for an excellent advice column and I’m looking forward to your response/advice, just hope it won’t be too expensive.

Tommy van Gent

A: I’m 99% sure that the rough idling and heavy fuel consumption is due to the TPS or Throttle Position Sensor as I’ve had a similar problem in my workshop before. A bigger and more costly issue is that the TPS for this bike can only be bought with the entire throttle body assembly costing over R10,000! However, I know the TPS can be used from an early Yamaha R1 on your ZX-12R, 2002 for example, using carbs. This will only cost around R800 and can be bought as a separate item, but you’ll have to have the bike correctly calibrated by a competent mechanic after fitting the new TPS, so you’ll have to find one in your area.

If you fit any performance camshaft to a bike it will tend to make the bike a bit ‘lumpy’ at low rpm depending on camshaft duration and lift. But as a rule a fuel injected engine will not compensate for that.

The rim size of the ZX-12R is designed for a 190 tyre but you can run either a 180 or 200. But with the wider tyre, and with 5,00km of abuse, the centre section will become square more so than say, than a 190. This will definitely make the bike harder to turn, or need more effort to turn, and perhaps induce a slight weave when getting towards the end of its lifespan. So perhaps you should have stayed with a 190 and not been forced into buying a 200?

Finally, you will need a complete clutch kit to cure your slipping problem, which includes friction plates and steel plates. When the friction plates wear after a lot of kilometers the steel plates will also become blue and probably buckled, so I’m afraid a new clutch is what you need to buy. It might also pay to fit a new set of clutch springs while you’re at it. Hope this answers all of your questions Tommy?

Q: I own a Honda VTR SP1 and it has an annoying hesitation problem. It happens at low rpm when I open the throttle and also while cruising. I’ve checked out and done the following tasks but I still can’t seem to find the problem:

1: I inspected the iridium plugs for a strong spark and correct gap.

2: I checked the fuel filter, which was very dirty. I first cleaned it out and then decided to fit a new one as the bike has 43,000km on the clock.

3: Due to the dirty filter I was concerned about blocked injectors so I removed them and did a flow check using a separate power supply, they all seemed to be OK.

4: I later found that the vacuum pipe on the engine was off. I thought that might be the problem but when pushed back on, the bike’s hesitation was still there.

5: I’ve removed and cleaned all the electrical connectors I can find but, and yes you’ve guessed; the bike is still giving me trouble.

So I would really appreciate it if you could give me any advice to send me in the right direction, and thanks?

Kobus Scheepers

A: Unfortunately Kobus this particular question is nigh on impossible to answer by words alone. The SP1 is a very complicated motorcycle, too much so in most areas, and is therefore pretty horrible to work on. The amount of kilometers your bike has covered lifts my left eyebrow as sometimes a bike of this age just tends to ‘go off’.

For example, on the right hand side of the rear sub-frame is the fuel injection control unit, which might be the problem, but there’re no test procedures for this unit. See what I mean now?

But, you could just opt to fit a Power Commander or similar which should cure the problem if set up correctly. That’s about the best advice I can give you without having the bike with me, which sadly I’d prefer not to, as it could take forever to find the problem and the labour cost would therefore be way too high.

Q: Hi guys,

At the moment I have a problem with my Suzuki TL 1000 S. After having it recently serviced I was informed that the cable controlling the idling speed had broken, probably due to age. I was informed that it wouldn’t give me any problems and I could ride the bike while a cable was sourced and then fitted.

The bike was fine for the first week or so and then suddenly she started misbehaving, as in an annoying misfire, and shortly after it began to stall as I approached the robots.

To cut a long story short she was throwing too much fuel into the front cylinder making the bike feel like it was only running on one cylinder.

I’ve had the valve clearances checked, as was the fuel filter, fuel pump and, the injectors were taken out and cleaned, but there’s still no improvement.

At this point in time I’m thinking ECU, is there any way to test it for any faults? I hope it’s not this black box as they cost a ridiculous R14,800 from Suzuki SA!

Can you please assist me as I love this machine and I’ve now been waiting over a month with little progress made?

Hennie Cloete   Hazyview  e-mail

A: I wouldn’t concern myself with the ECU, as that would give different symptoms. And don’t worry about that cable either; all it does is move a cam around to alter the idle speed.

I would take a look at the throttle position sensor though, which sits on the side of the throttle bodies. They do tend to malfunction on older bikes and give the sort of problems that you’ve described. It should only cost around R800, but it will have to be installed correctly and recalibrated before riding, either by you using a genuine workshop manual or by a qualified mechanic. I’d be surprised if that didn’t cure this annoying fault on your beloved TL 1000 S. Let me know?