1978 GS1000 bored out to 1173 by RC Engineering

[terry]

G'Day Jack, that bike looks brilliant mate! The gerex ignition arrived yesterday, thanks for that mate, your bigger cooler must be very close to arriving in CA, so I hope you like it! (Does anyone here know how to fit and time one of these ignitions?)

I think you've inspired me to rebuild the remains of my 1979 GS1000SN, I've got enough bits to build it now, I bought a NOS Wiseco 1170 kit for it recently, have a pair of "Ivan Tighe" race cams, a later "big port" head, some 34mm Mikuni flat slide carbs, (I'd prefer 36's, but these supposedly flow better than 33mm smooth-bores, so should be up to the task) etc etc.

I do, however, need a pipe for it, do you still have the old one off your bike, and if so, would you like to sell it? I'm getting an old CB750 Supertrapp pipe ceramic coated by HPC Coatings in the "brushed alloy" color, and they'll give me a discount if I get them to do another pipe at the same time, so I thought, why not? Let me know mate?

Also, did all the 1978 bikes run alloy rims like yours? I'd love a pair of them too, I'm not keen on the current 17 inch rim fashion, I understand the technical advantages re: fitting modern tires etc, but don't much like the look? Have a good one Jack, Cheers, Terry.

 

[dsw1953]

Sounds very nice

 

[KEITH KRAUSE]

The 75/80 steering wobble is most commonly caused by loose steering bearings. Shaking the front end doesn't always expose it. After my restoration, I thought I had the bearings torqued pretty good. First time over 80 the bars wobbled without warning and scared heck out of me.
Loosen the center bolt, center bolt pinch bolt on the side and the upper fork pinch bolts. Make a mark with a marker to record where the steering stem nut is now set. Try 1/8 turn tighter on the nut, tighten everything and test. Repeat if necessary. I tighten the center bolt and side bolt first, then the fork pinch bolts. Top center bolt torque is 36 ft/lb I believe.
With the bike on the centerstand and wheel off the ground, the bars should turn side to side with just a little drag.
If you do find that tightening doesn't help (I doubt it) then you can return the steering nut to where it was (the marks) and search elsewhere for the reason.
There is a factory steering stem torquing procedure but it seems incorrect to me and I can't follow it (tried back in '80 and gave up ever since making sense of it). It's based on the steering nut being tightened within a certain range and then backing off the center bolt(?) but it's too vague to bother with. The method I use above results in the same adjustment anyway. Works for me.

 

[terry]

G'Day Keith, is there a possibility that the steering head bearings are worn out?

I'm just thinking that even though they're ultra-tough tapered rollers, like most things that don't cause us trouble, they probably get very little in the way of maintenance?

I don't want to admit it, but my steering head bearings are probably still circulating in the OEM grease from 1981?

I'm just thinking that if there is some wear in them, adjusting them may not make any difference? I'd hate Jack to assume that his steering head bearings aren't the culprit, and start looking elsewhere, when it's possible that they're cactus? Cheers, Terry.

 

[KEITH KRAUSE]

Yes, the bearings could be bad as you say.
I have a feeling they're good and tightening them down will get rid of his wobble. Tapered bearings are very tough as you mentioned.
When I said if tightening doesn't help to "look elsewhere", I could have used better words. Bearing wear could be still be possible, along with many other things that cause wobble.
I suppose I'm just basing my advice on past experience and the likeliness of what may be wrong. Loose bearings first, worn bearings somewhere down the list with a lot of other possibilities.

 

[Guest]

Keith, thanks as always for your insight. I'm inclined to believe you're right about tightening the steering head. The bearings themselves are probably in pretty decent shape; the bike has less than 9,000 miles on the clock. In comparing my single front disk 1000 against this bike, I'm interested in knowing why the double disk wheel feels so much lighter. I know the rotors are drilled, but you'd think the extra caliper and rotor would offset the weight savings. I'm guessing a lighter front end and loose steering head bearings is a bad combo. The day after Thanksgiving I'll belch a few times and try your technique. . . I'll let you know how it works.

Terry, the old Supertrapp race header was rusty and holed like a cheese grater and is probably being melted down to make corned-beef hash cans even as we speak. Amazed the old ignition got to you so fast. Stay tuned for future wheel developments.

 

[KEITH KRAUSE]

Well, it isn't really my technique, just basically tightening the stem more than you have it right now.
It's common to feel no play/slop in the front end but once you go down the road at speed...uh oh!
So 1/8 turn at first is what I'd try. If it improves but doesn't completely go away, them maybe another 1/8 or even less than that might do it.
Just as long as the bars don't start dragging too much. The bars/drag will tell you when you're tightening to much.
As for loosening the fork pinch bolts, it's always made sense to me. If you loosen only the center and side pinch bolt, then tighten the steering nut down some, re-tightening only the center bolt will cause the upper bracket/clamp to possibly bind/flex. The upper clamp should go straight down and evenly, not just down more near the front.
Some people get anal about it and loosen the lower fork pinch bolts too. I will too, if I see that the forks tops no longer align flush with the top of the upper bracket/clamp after the additional tightening.

 

[terry]

Terry, the old Supertrapp race header was rusty and holed like a cheese grater and is probably being melted down to make corned-beef hash cans even as we speak. Amazed the old ignition got to you so fast. Stay tuned for future wheel developments.

No worries Jack, thanks for that, and if you see a spare set of those alloy rimmed wheels lying around, let me know mate? Cheers, Terry.

 

[KEITH KRAUSE]

Also, I've never weighed the "E" front wheel assembly against the spoked/single disc assembly, but I'd have to believe the dual disc/cast wheel E model weighs more.
Seems like the only way the E model could feel lighter is if it's more solid or something's wrong with the spoked front end, such as something loose. I know low tire pressure can give you that heavy feeling, along with loose parts.

 

[Guest]

Did my first valve adjustment a month ago. I could see right away that underside of the cam cover had been ground in places to accommodate the high-lift cams.

Engraved at the end of the intake camshaft were the numerals .515 and, of course, R.C. Engineering.

What does that figure represent?

Thanks in advance,

Jack

 

[salty_monk]

It's wrong to be a duration figure so perhaps it is maximum lift in inches??

Dan

 

[Big T]

Also, did all the 1978 bikes run alloy rims like yours? I'd love a pair of them too, I'm not keen on the current 17 inch rim fashion, I understand the technical advantages re: fitting modern tires etc, but don't much like the look? Have a good one Jack, Cheers, Terry.

The US had 2 models in 1978, the standard (sometimes called the C) with wire wheels and one front disc. It came in red (like Jack's) and blue (like mine)

The E model (aka Skunk) was black with a white stripe, cast wheels, 2 front discs and some other minor differences, like a 17" rear wheel

The GS1000 had standard aluminum rims, which is nice. They had standard plated spokes, which is bad. I've had both of mine converted to Buchanons SS spokes. I see spoked wheels regularly on Ebay for reasonable costs.

Jacks has an E model fork, calipers and discs mated to the wire wheel.

Beautiful bike, Jack!

 

[BadBillyB]

Did my first valve adjustment a month ago. I could see right away that underside of the cam cover had been ground in places to accommodate the high-lift cams.

Engraved at the end of the intake camshaft were the numerals .515 and, of course, R.C. Engineering.

What does that figure represent?

Thanks in advance,

Jack

When you adjusted the valves, were the shims on top of the cam follower like stock ????.....In order to run higher than .400" lift cams, the 650 Kaw style cam followers with the small shim underneath MUST be used......Billy

 

[Guest]

The shims were sitting under the cam lobes, just like stock.