HI, I just did a valve adjust and balanced the throttle body's on my 86 k100 and it is the most rewarding thing I have ever done on any vehicle I have ever had! she runs great, winds right up with way less vibration.


Brian

That's interesting to hear. Was it really that noticeable an improvement?
I'm just about to order myself the valve adjustment tool and a few shims. Motobins do a set of 8 of the most common sizes for about £17. Already have the gauges.
Checked the valves last year and a couple were a bit tight.
Seemed to be nearly impossible to sync the injectors if the clearances are out.
My K has 40K miles but I remember riding one when they were new and would love to get something approaching that smoothness.

Yankeeone, I'd be curious as to how you accomplished the throttle body sync. It's easily done at idle with vacuum sticks (or other gages) by adjusting of the air screws. Of course this'll do nothing for the engine running at any rpm a bit above idle. Were the valve clearances tight at all? Mine never seem to change. They're always right in the middle of the specified range.

HI, I used the tube in a long u shape around a yard stick with mystery oil as the "Mercury" method to do the balance. When I did the valve adj. the Three of the intake valves were out by .05mm. Two ex.were tight by .05mm, one ex. was out by .10 mm. When I rode the bike for the first time after the adj. I was worried that I messed something up,but I planned to balance, the throttle bodies when I was able to warm it up (snow finally off the roads) I put one tube of the gauge on the front cylinder put the 2nd on the next and set the cylinders by turn to the first one, three of them were within 1/4 turn but the last was more than a full turn out! I did not notice much change in the idle but the bike ran much smoother all the way up to red line, before the work I did not feel right in the higher rpm, even when cruising at 4500-6000 it was just not right. I think it feels similar to when you get new tires on the car, you realize how bad the old ones were.There is a utube out there that shows how to make the "manometer."

Brian

Hi Brian. I think TWB thought you had tweeked the throttle linkages. A big no no unless someone has already had a go and there's nothing to lose.
His comments about the air bleed screws only affecting tickover started me thinking.
While the effect would be negligible at large throttle openings, how often do we whack the twistgrip wide open?
If crusing at 50 or 60mph, how far is the twistgrip turned open? Not a lot.
This means the vacuum in the inlet manifold is increased which also increases the volume of air coming via the bleed port.
So... while they may not make any difference when nailing it, there is a possibility it may cause more vibration when crusing at small openings, if out of adjustment.
Regarding valve clearances, I think TWB has been lucky so far. At least two of mine need adjusted after 40k miles, although I don't think its going to be a frequent issue.

Good info Brian. This is next on my list after getting the FI and everything back in the bike. Was going to buy a sync tool, but now you got me thinking it might be a good DIY project and put the money towards other parts.

Hi Oldgoat.
Check out the Carbtune Pro from carbtune.co.uk.
Works well on any K bike and they supply to the States for only $95 including P&P.
And it comes from Belfast!

1+ on the carbtune.
Nice piece of gear to sync your flow.
Got one and happy with it.
Cheers,Wikur!

This is what I use. Since it's obviously not for four cylinder applications, at idle I connect it to the vacuum ports on cylinders one and four, then two and three, and so on, comparing the pulses. The sensitivity is adjustable. She ticks over like a 1,000 rpm metronome.

Thanks for the recommendations guys. I ended up going with the TwinMax.

I was having a sticky beak round the place to see if I could find some clarification about the subject when I stumbled upon this person's description of the effort required to effectively 'sync' the K-bike's throttle bodies at anything above idle. have a read of his comments. It's not to be done easily, me thinks. Just stick with twiddling the airscrews using a Mercury carbstick set, vacuum gages or somesuch other apparatus.

"Well, as it turns out, I did go there with my old K100RT (same throttle
body as your bike has, Vox). The reason I had to rebalance the throttle
bodies was that the twit of a previous owner had played with the
adjustment, thinking he could do a better job than the Bing factory.

What I did was to drive a big Gast high volume rotary vane vacuum pump
with a 1/3 HP motor and draw a high volume of air through each throttle
body (one at a time) noting vacuum on each one at various low throttle
openings.

It was a bitch to get right, since, slightly adjusting one throttle body can affect the others.

In the end, after several hours of work, I managed it. The result was a
smoother idle and slightly better low-throttle performance. Under higher
load, of course, there was no change in performance, but none should be
expected, since the tiny changes in butterfly angle needed to balance
the throttle bodies at closed or near-closed position, are far too
insignificant to make any noticeable alteration to airflow at 1/4
throttle or more.

My basic point above was that first, even if the throttle bodies somehow
managed to get out slightly of alignment, all it affects is idle and
maybe some low-throttle smoothness. Hardly worth the effort.... unless
one has a bike that has been previously mucked around with."
~Bob, from Vancouver
(but I dunno which one)

I dont know the "theory" behind the balancing of the intakes with the air screws, but I know that before I balanced mine there was quite a vibration almost all the way thru the rpm range , after, none, I wonder if someone out there would like to do a test , mark one or two adj, screws change the setting, test ride the bike see how she feels. report back.

Brian

hmm ...sounds like a nice subjective test brian ......i would be interested to see the results also

Could be as simple as the valve clearances were out and getting them right has made your bike smoother rather than the air bleed screws.

Well the thing is, the valves were out, and I rode the bike after the adj. that's when the vibrations were bad , so I went about 10 miles to warm the bike up, then did the air screw balance = bike smooth thru the rpm range.

Brian

Hi Brian,
That's excellent news and if as you found it reduces vibrations that is well worth doing. good on you for letting us know.
Regards,
K-BIKE