Revving it at standstill.

[Geodude]

Originally Posted by Spanner Man

Good morning all.


Now for my fourpence worth!

It's all a question of throttle response Darlings. The fewer the cylinders an engine has, the longer it takes to respond to a fistful. This is because it's 'bangs' are further apart, than on an engine with more cylinders. Hence it takes longer (in fractions of a second) to overcome the inertia of the engines internals.
If an engine is not fully warmed up, the percentage of un burnt fuel per firing stroke is greater. Therefore giving it a fistful when it's cold or semi warm, effectively gives the spark plugs a bit of a soaking. This is commonly referred to as bogging down.


Cheers.


P.S. It's not a good idea to rev the B@LL@cks of an engine that's not under load in any case, & doing it when the engine is cold will accelerate engine wear further.

Yet another question of mine answered cheers

[Spanner Man]

Originally Posted by fastdruid

Agreed, its also not a good idea to let it idle either...

Idle is just about the worst possible for cam loading and oil flow. There is a sweet spot for warming up it depends on the bike but for example HRC say to warm up the NC30/35 at 5-6 k as this gives the least cam loading without reving it too high.

Druid

Couldn't have put it better myself old Boy!

An engine warms up more quickly when under a light load. Therefore it's better to ride it gently when cold. than to let it idle for England. & let's not forget, that for every 5 minutes of idling, a Koala dies!


Cheers.


P.S. A pleasure geodude!

Originally Posted by Spanner Man

Couldn't have put it better myself old Boy!

An engine warms up more quickly when under a light load. Therefore it's better to ride it gently when cold. than to let it idle for England. & let's not forget, that for every 5 minutes of idling, a Koala dies!


Cheers.


P.S. A pleasure geodude!

Hurray! I don't have to stand about warming the bike up. Best news I've had all year. Just keep the revs down for the first couple of miles. Why the hell don't they tell you this in the manual?

Bit of a side-track here but still on topic, to do with warming up engines sort of

Being a honda V4 geekazoid (but not as much as fastdruid, and probably still not as much as spannerman) I read the honda V4 book written by julian ryder in one sitting, and Mr Ryder recalls the story of early honda VF's having incured major engine faliure, as a result of excessive camshaft wear. Honda never came across this in their testing, since it was reported that the test riders would warm their engines up "properly"...Mr Ryder dosn;t state what this means, but I assume it means allowing the bike to reach is optimum running tempurature (85 deg.C or so?) before setting off. Apparently, the problem was due to the camshaft bearings...I don;t know the technical terms so someone will have to help me out here, but the part you bolt down ontop of the camshaft was made in a completly differant place to the bottom part, so the two parts where never perfeclty (as much as perfect can get on a mass-produced head) mated. There was enough free play / clearance that the cam shafts would move around and pretty much wear themselves out after a few thousand miles; a typical owner started his/her bike on choke, probably let it run at a fast idle for about 20 seconds beore knocking it off and going for their ride. I suppose with these cold parts, the tolerances where even much worse than when warm and further accelerated the wear.

Something else I remember from that book; honda engineers would fill the bikes up with oil, and let the testers go out and ride them. They'd only change the oil 20,000 miles later.

Originally Posted by Alpinestarhero

... Apparently, the problem was due to the camshaft bearings...I don;t know the technical terms so someone will have to help me out here, but the part you bolt down ontop of the camshaft was made in a completly differant place to the bottom part, so the two parts where never perfeclty (as much as perfect can get on a mass-produced head) mated. There was enough free play / clearance that the cam shafts would move around and pretty much wear themselves out after a few thousand miles ....

That sounds a bit weird. Is that right? I am not sure what they're doing these days, but I come from a time when bearing caps /top cover were always mated as a machined set to the head. ie caps are bolted in position prior to boring of camshaft tunnel and are not interchangeable between heads.

Originally Posted by MattCollins

That sounds a bit weird. Is that right? I am not sure what they're doing these days, but I come from a time when bearing caps /top cover were always mated as a machined set to the head. ie caps are bolted in position prior to boring of camshaft tunnel and are not interchangeable between heads.

Well, that was the point; honda started doing it differantly, i don't know why...maybe it was easier / quicker? Either way, it ended up costing them dearly and they went back to doing it the proper way. One of those things where honda got over-confident (read: cocky)

[fastdruid]

Originally Posted by Alpinestarhero

Apparently, the problem was due to the camshaft bearings...I don;t know the technical terms so someone will have to help me out here, but the part you bolt down ontop of the camshaft was made in a completly differant place to the bottom part, so the two parts where never perfeclty (as much as perfect can get on a mass-produced head) mated.

Most are line bored, ie you bolt everthing together, then bore (ie drill) it through in one sweep, ensures that everything is inline. The VF750 apparently had too small holders, the VF500 had larger ones and didn't suffer as much.

There was enough free play / clearance that the cam shafts would move around and pretty much wear themselves out after a few thousand miles; a typical owner started his/her bike on choke, probably let it run at a fast idle for about 20 seconds beore knocking it off and going for their ride. I suppose with these cold parts, the tolerances where even much worse than when warm and further accelerated the wear.

IIRC the problem was a multiple one, not that simple but was essentially up to 6 things in combination.

1) Forked followers - they tilt when adjusting valve clearances (fix was to use two feeler gauges)
2) variation in cam to bearing clearances - needs a special tool to hold the camshaft[1]
3) Poor camchain tensioner
4) Soft cams
5) Heat - the V4 gets very very hot, rear cams apparently go first.
6) Poor lubrication.

Druid

[1] To combat this, Honda developed a special tool to hold the cam in place. Any bike shop tuning a V4 had better have this tool. It doesn't cost much ($15) and isn't hard to use. Get one; even though it doesn't completely solve the problem, it is a requirement. Part number is 07979-MK30000, name is "V4 tappet adjust". The service bulletin issued with this tool recommends valve clearance of .006 inches instead of .005 that the Sabre/Magna originally specified, as well as use of premium motorcycle oil, changed frequently, and avoidance of prolonged idling.

[Biker Biggles]

I thought it was just a metalurgy issue with poor quality metals or poor case hardening?????
The issue with cam caps sounds a bit like a problem they had with the CBR600 about 98/99 when there was an issue with the caps not quite seating properly after valve clearence checks.Or is my memory playing up with age???

Originally Posted by fastdruid

3) Poor camchain tensioner

but thats a honda characteristic anyway

Thankyou for the extra information there Cheif V4

[fastdruid]

Originally Posted by Alpinestarhero

but thats a honda characteristic anyway

Eh? I have 4 honda's in my garage and not a single camchain tensioner between them. For that matter not a single camchain between them.

Druid