Topic: Am I killing my bike or is it really that fast?

[HondaJay]

About a month ago I bought a 1980 Cb 650 that needed some serious work.  After working on it for several hours a day for a week I had it running.  The only problem is I dont have a tach gear so I dont know how fast the engine is going.

I thought I remembered seeing somewhere that it topped out in first gear at around 45mph so I started with that and have been going by sound when I ride it.

Then yesterday I was out riding and decided to go ahead and let it go in first until it backed off on its own.......  I never expected to hit over 60mph(!!!!) before shifting into second and taking it up to about 90 in second.

When I got home I looked through all my manuals and notes and wasnt able to find the gearing chart I was thinking of and searching online wasnt very helpful either.

So.... is my memory failing me, or did I just run my bike up to around 14,000rpm?

It came with a Kerker 4-1 exhaust and an aftermarket cam plus I replaced the intake system with 4 k&n pod filters so i expected it might be able to run a little higher rpm than stock but something here doesnt seem right.

[Pinhead]

I don't know about your particular RPM/speed ratio, but since you've gotgot 4 pods and 4-1 exhaust I would expect the motor to run like crazy if it's tuned right. My '79 650 runs a LOT better since I opened up my intake manifold and slightly opened my exhaust. If your 4-1 is more open than my stock 4-2's are (I assume they are) that 650 should run pretty darn good.

[Gordon]

Then yesterday I was out riding and decided to go ahead and let it go in first until it backed off on its own.......  I never expected to hit over 60mph(!!!!) before shifting into second and taking it up to about 90 in second.

I wouldn't suggest doing that very often.

[Ibsen]

I think you might be killing it.  On the other hand, you have reached some impressive speeds though. 

Red line is at 9500 rpm, and this is the top speed at red line in the different gears with a standard 16 front - 40 rear sprocket gearing:

1. gear  42 mph
2.   "     61  "
3.   "     77  "
4.   "     96  "
5.   "    119 " 

[flatblack]

<clearing throat>

Ummm, perhaps the speedo is a tad fubar'd? Borrow a portable GPS and clock it.

Until then, if the engine seems like it's nearing its rev limit, upshift. No good reason to flog a 25-year-old street motor.

fb

[kghost]

<Snorts of laughter>

Hey! buy a tach.

[750goes]

If the bike needed some serious work, did you lubricate that speedo cable at all - it may well be giving you some false impressions, but if it does run to 60 in first - don't try to improve on that....

[Ernie]

<Snorts of laughter>

Hey! buy a tach.

if you wanna keep that motor id buy a tachometer with the correct redline too

[cb650]

I have a few it your interested.




              Terry

[HondaJay]

To reply to all of your posts....

I dont plan on doing that very often (or ever again now that I know I was right about the gearing).  I just got an 06 crb1000rr for when I want to go fast (almost 100 in first gear, 9.8 1/4 mile @ 146mph ) but I still love the classics and working on them.

Thanks a lot for the redline speeds, I knew I had seen that somewhere but I couldnt find it when I looked

The speedo is working well and is decently accurate (GPS read 57 when my speedo was at 60)

I have a working tach and cable; the part i need is the actual gear that goes inside the engine.  I found a place where I can order one but they wanted over $30 for it and I dont need it that bad.  If anyone has one in decent condition I might be willing to take it off your hands for a reasonable price.

Thanks!
J

[Jerry Rxman Griffin aka MuthaF'er]

My thoughts are if you are pulling 90 in 2nd gear and the 90 part is correct then you have had your gearing changed. I can get 100 out of 3rd on my 75 750F if I try hard and really wind it but I won't do that very often. its had engine mods due to winding too high and breaking a valve. Get a tach !

[RSV12K]

I don't care what anyone says, that bike did not see anything close to 14K or it (and maybe you) would have seen God.