Thunderace temp gauge and rev counter, Help ?

[Snakeskin74]

Hi, I have just bought a Yamaha Thunderace, the bike has a f/s/h and the guy selling seemed genuine ! It was poring down with rain when I looked at it, so I broke the cardinal rule and put down a deposit without test riding it first

Riding home I looked down at my rev counter and it reads what I am doing, then the needle jumps up to 7,000rpm, then drops down to 0, and then back to what ever I am doing. This repeats over and over all the way home (32 miles). I then noticed that the temp gauge doesnt work at all

So does anyone have any idea whats going on, do I need to replace the hole clocks panel (losing the genuine mileage) or is it something that can be fixed.

Thanks in advance.

[Voodoo]

Sounds to me like a loose connection or water ingress in one of the connectors. Firstly I'd wait until its dry and then start checking the connectors one by one.

[Snakeskin74]

Sounds to me like a loose connection or water ingress in one of the connectors. Firstly I'd wait until its dry and then start checking the connectors one by one.

Oh could be as simple as that, thank you.

[mattycoops43]

WD40 is your friend!

[Snakeskin74]

WD40 is your friend!

I agree, it came in handy for my K2 Gixxer, the headlights worked one minute and not the other. That turned out to be a box conecter that was corroded.

[Snakeskin74]

Ive just joined a Thunderace owners club, and this is what I have found.

The rev counter on the Ace also doubles as a diagnostic unit in that it will show higher revs for a few seconds to indicate a problem with certain things.

So here they are

3000rpm means a problem with the throttle position sensor

7000rpm means a problem with the EXUP valve or motor

and 8000rpm indicates a problem with the fuel level indicator circuit

[Voodoo]

A lot of bikes do that, but I always thought its as you first turn the key on, and then after a few seconds it settles back down (before you start the engine). In other words it wouldn't be doing it whilst you were riding. Obviously I'm no expert and could be completely wrong but it would seem a little stupid to me that the manufacturers turn the rev counter into a diagnostic computer and then leave it like that until the problems fixed.

If it were my bike, I'd take off the clocks and check the connections behind and see if that makes any difference before I started spending money.

If that makes no difference, then I'd probably go along the route of fixing the temp gauge first because they are quite simplistic in the way they work, and I suspect its related somehow. With the temp gauge its quite easy to check the sensor and thermostat (without replacing them) which would then eliminate them as a problem, which would then leave either the wiring or the actual gauge. You could then test the wiring with a multi-meter and you'd then know if its either the gauge or the wiring.

Again I'm no expert, just tight fisted, so I always start with the least expensive option.

Whilst your checking stuff, the EXUP valve is also quite easy to check if its seized. I'm assuming you know where its located (on the exhaust under the engine) and there should be some cables going to it which turn it. I also assume it should open and close the valve as soon as you turn the keys on (before the engine has started) which you should hear, but you should also be able to see movement.

[Snakeskin74]

Hi voodoo, thanks for taking the time to help. I have a haynes manual for the bike, and it is true that the rev counter does double up as a diagnostic. I took it in to a garage this afternoon, and they said the same. As far as the temp gauge, they said what you are saying.

However the worst thing is, I asked them to check the rear shock, and they said it was totaly f##cked ! So I need to find a secound hand one, because a new one would be 300 quid.

[eastanglianbiker]

is it definatly the shock itself as they have a habit of the linkages seizing up same as the earlier fzr range did,hope you get it sorted out soon

[Snakeskin74]

is it definatly the shock itself as they have a habit of the linkages seizing up same as the earlier fzr range did,hope you get it sorted out soon

I dont know, I have asked the question on the thunderace forum, see what they say. Thanks for your help.

[Voodoo]

Not sure what your like at getting your hands dirty, but if it was me I'd take the shock off first, clean it up and grease it and see it that makes a difference. Like eastanglianbiker says, it could be seized linkages. The most difficult bit is raising the rear of the bike off the ground (without using a paddock stand) unless its got a centre stand of course, which I doubt.

Failing that my next step would be to look for another shock. There is a secondhand shock on ebay at the moment for £50 plus £15 delivery, although you don't know if that's knackered too, so I would be tempted to get one of the reconditioned ones for about £100.

Just out of interest though, why did they think its knackered, is it because its just bouncing back up or is it not rising back up at all, or is it because they couldn't adjust it?

[Snakeskin74]

Well I new it wasnt right, because when riding the bike, it feels clunky and theres just no damping to speak of. When I went to the shop, I just asked him want he thought of the rear shock, so all he did was push down on the back end of the bike, trying to bump it up and down, and put simply he said it was knackerd.

[Snakeskin74]

Hi, just a quick update, well I have taken the shock off, and taken it to a specialist, who is doing a complete service on it, including a new piston rod, 175 quid.

I have sorted the rev counter code, by removing the ex-up valve cables, so the servo is going through the motions without any resistance from the valve. I am going to replace the whole exhaust system anyway, so no need for the ex-up.

Temp gauge turned out to be a bad earth, so thats fixed now.

[Snakeskin74]

Oh and I have just ordered a pair of fork legs as well.