What is this a sign of?

[Rob W]

On my bike (ZXR4) it's always been that every 1000rpm in top was bang on 10mph, so obviously 4000rpm was 40mph.

Just recently I've noticed that it's pulling slightly more revs to get the same speed, as in 40mph is now about 4500-4750rpm. Is this a sign of something wearing on the bike like the valves or whatever, or is it just one of those things? I've only recently noticed it, and just wondered if it could be a warning that something was up. Other than that the bike is riding perfectly.

Cheers.
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'90 TS50 > '04 Senda 125 > '91 ZXR400 > '90 CB-1 > '04 GSX-R1000 > '96 Bandit 600 > '89 ZXR750 H1 > '96 GSX-R750 SRAD > '98 RR-W Fireblade > '98 T595 Daytona > '03 Hornet 900 > '04 Fireblade > '16 GSX-S1000F (x2) > '23 XSR900

[Barry_M2]

Mean's your in 5th and not 6th!

Probably just an inacurate tacho. Could be a dodgy connection as tacho is electrical.

Wouldn't be engine wear.

[stinkwheel]

More likely the speedo cable needs oiling or you have fitted a tyre with a different profile which has affected the speedo reading.

Could also be caused by clutch slip but this wouldn't be constant and you should be able to feel it happening.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[mr.z]

Yeh if they taco/speedo cables were new when you first compared they do go off by quite a bit..

Could be the air filter is slightly blocked or wet.. could even be the weather has warmed up quite a bit? (colder air is more dense, so you tend to get more power in certain condtions when its cold)

Unbalanced carbs? tappets off? looseing compression on one cylinder? could be soooo many things..
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>RidingSkills<->Tech Tips<->MyBikes<

[stinkwheel]

It shouldn't really be anything to do with the mechanical function of the engine. The gearing is all fixed in terms of when the engine turns over once, it moved the gearbox by a certain amount which turns the gearbox a certain amount. There is no room for slippage/ variation. x rpm = y mph and always will do unless you change the number of teeth on one of the gears.

Even if it was running on one cylinder and spewing oil all over the road with a conrod sticking out through the side of the engine, the revs and speed would match.

The only place there is room for slippage is in the clutch which you would notice. If this isn't the case then either your tacho or speedo is lying to you.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Rob W]

Cheers for all the replies lads, .

The reason I asked is that when me and my dad were twatting through the lanes at Burnham yesterday I noticed that it was revving slightly more than it used to, and the old girl was basically being thrashed constantly for about half an hour or so, and I didn't like the idea thinking that at any minute my engine was about to explode (it probably wasn't far from it).


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'90 TS50 > '04 Senda 125 > '91 ZXR400 > '90 CB-1 > '04 GSX-R1000 > '96 Bandit 600 > '89 ZXR750 H1 > '96 GSX-R750 SRAD > '98 RR-W Fireblade > '98 T595 Daytona > '03 Hornet 900 > '04 Fireblade > '16 GSX-S1000F (x2) > '23 XSR900

[Rob W]

[feef]

[ZRX61]

[mr.z]

Lick my balls mr grumpy arse, not everyone here is a fully seasoned mechanic, just trying to help

Inretrospect yes that post was arse but hey, live and learn..
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>RidingSkills<->Tech Tips<->MyBikes<