I'm probably not going to get too far with this, but here goes...

For the real gear-heads on here, has anyone had any luck trying to increase the valve overlap?

I'm going to make a tool in order to mount a degree wheel so I can get a reading on valve position,

but I took some quick measurement just using a dial indicator to find TDC, then checked the overlap measurements on the intake & exhaust valves.

Because my cam chain is no doubt stretched, I got + .073" on the intake valve @TDC and .112" on the exhaust valve.

I would like to set the cams up to be about equal at about +.100" for both the intake & exhaust valve @TDC.

If you're not familiar with this method, I understand, most guys work with lobe centers, but I've worked through that tedious process so many times, I have moved on to this simpler method.

So, has anyone here ever even seen or heard of adjustable cam sprokets for the K-100?

Thanks,

Rick

I dont know of anyone who has played with that but have often considered it myself. It wouldn't be a difficult job with just one locating pin, a set of vernier sprockets could be made.
It's truely amazing just how much can be gained from a bit of a tweak here and there.

To be honest, I am thinking of grinding off the locating pin, that way I can rotate the sprocket as needed, then I will use green loctite on the washer / sprocket / bolt to prevent movement once I'm done.

I thought about using a bigger diameter washer to add some additional surface pressure to the sprocket from the bolt.

I have gotten fairly amazing results in the past, and the results I'm refering to were dynamometer tested.

Most Japanese bikes especially the older 8 valve units were very conservatively timed, usually the exhaust cam timing was where most of the power was hiding.

I no longer have my dyno though, so I'll be tested via seat of the pants.



Rick

hmm a great thread !!

a set washer possibly position located and locked to the camshaft with a half moon type lobe arangement would be better than relying on locktight ....possibly after finding the location for test, a tap could be run through both the locked washer and the cam wheel and locked off with an appropriate bolt .....4mm perhaps

yes agree that most bikes are "detuned " when put into production ....from the developed engine with real spark, i guess its how they keep them running for more than the warranty period .

Charlie, yes your idea would be safer, so...better.

Thanks.



Rick

I am just thinking of a vernier adjuster. I cant come up with the real figures but say 16 deg per tooth on the cam sprocket then drill 15 holes for the pin at equal points and you have 1 deg adjustments without any pain at all.
We used to elongate the holes for the 900 Kawasakis I drag raced but they didn't always hold because of cast sprockets cracking etc often leading to some disasterous outcomes. The K100 lend themselves to a much better system with the single pin.

Sorry, but never heard about. What is a gain with that method. Expensive?

For an example, look at an early Alfa Romeo Guillietta engine, or workshop manual. They were twin overhead camshaft with vernier adustable cam timing, I remember seeing one on a bench in the mid seventy's. They had a pin system from memory, not sure how many increments. Those engines used twin Delorto carbs, much different to EFI, which have camshafts specifically matched to the whole management system. I'm wondering if you may be investing a lot of time and effort for little or no gain. Maybe look for a set of '85 camshafts, they were a little different I think ???

There are details of my degree plate setup in this thread:-http://k100rt.aforumfree.com/t3402-tdc-tool
Cheers,
Paul.

Ok, so I set-up my degree wheel, and checked the stock cam timing.

What I basically wanted to know was the intake & exhaust valves position on over-lap @ TDC.

That is where, at TDC both valves are open, being intake opening, exhaust closing.

(I realize that some of you do not need all of this explained, but some might)

What I found out surprised me, it seems waaay back then in 1985 the engineers at BMW knew what would work pretty well.

The intake valve was open .090" @TDC and the exhaust was open .095" @TDC.

Those are very good numbers especially for an injected engine.

Also, each valve was still quite conservative in that they both had over .100" VP clearance at that TDC opening.

Now, if I did not have to do a lot of fiddling, and machining, I would probably have bumped them both a little further to +.100" .

Seriously though, the minimal gains would not be worth the effort.

In conclusion, unlike many Japanese 8 valve motors of this vintage, there would be little gain in modifying the cam timing from what I found.

I will however install a new cam chain, as I think mine is stretched, because I do hear a mysterious "ggrrrraaaaattt" type noise from somewhere down below when I trail the throttle, and I think it might just be my cam chain.

I will report any new findings of significance on my valve overlap with the new chain.



Rick

That's some juicy info, Rick. Thanks for posting your findings. I've often dreamt of hot cams, valves opening with a higher lift and longer duration, and at times it would seem by my disturbed sleep patterns to my bedtime partner that I'm having nightmares.



Oh, pardon, this isn't pillow talk.

good one rick ...wish i could put that back to degrees ...as thats what im farmiliar with

Charlie, what do you want to know then....opening & closing degrees?
You want to calculate the lobe centers?
I'll do that if you want, I remember that the intake cam was starting to open at 40* BTDC, after that I stopped watching those numbers as they are not relevant to my way of calculating timing.

It is interesting that BMW chose to set the cams with a good amount of overlap even though the engine is injected.
All that signal is usually reserved for a performance oriented tuning of carburated engines.

Rick

yes thats exactly the thing i was after ...the duration of the cam ...the lift in mm (although i could translate that from imperial ) and the start of the lift in degrees btdc on the inlet side bbdc on the exhaust

wow 40 before thats quite a number ... i usually see things like 9 before pretty commonly with durations of 240 -270 degrees (crank rotation) with "track" timings at 300 ...bit unuseable on the road though

some folks do the measurement at .050 of valve lift

Charlie 99, that 40* BTDC was at zero lift, it was actual cam lift start, so if you want I can do it from .050".
The actual total lift was (I think) .355", but I'll double check tomorrow when I get your other numbers.

Rick

Great work Rick,
Really excellent investigation thanks for what you have sent so far.
Regards,
K-BIKE

Oh I think i will clean out a few brain cells for this info, just awaiting with bated breath.

Hey, I know I was going to post some new numbers, but my life got in the way a bit.
I ordered a new cam chain & 1 shim, from MAX BMW, and as soon as it arrives I will finish the install.
When I started this, I knew I would do a valve adjustment, and most of mine were out a few thou.
The funny thing is, the shims are the same as my old Kawasaki's from 3 decades ago.
I had all but one in stock.

Rick

Charlie 99, I checked the numbers for you, but because I do not use your method of calculating camshaft info, I will post what I think you wanted.

If I got it wrong, no problem let me know how you want the readings.

Intake Cam measured @ .050" - opens = 9* BTDC, closes = 45* ABDC @ .050"

Ehaust Cam measured @ .050" - opens = 40* BBDC, closes = 12* ATDC @ .050"

Both cams measure a total actual lift of .360" lift, that part surprised me.

Now all that is with the old chain, I'm still watching the post for my replacement.



Rick

Are you using a 1985 cam or later. I belive the 1985 cam is different then the later ones and was told the 85 cam was considered a hotter cam with more lift and duration. I never compared them side by side.

wow ...that is exactly the thing i was hoping to see rick

you wouldnt believe it ...but those numbers exactly line up with the hot toyota 1600 motor "high compression "motor of the ae92 the engines starting production date in 82 out of japan ...the rest of their motors maybe 60 odd killowatt units ...the "age" designated motors got a new head and cam timing of 240 degreees with 16 valves which took it to about 100 killowatts at the crank, the most famous being the ae86 from "tokyo drift" and ""sprinter" fame == tuned up were making about 200 horsepower with the 300 degree cams n/a ...or 230-240 degree cams and a turbo for a bit more .

Intake Cam measured @ .050" - opens = 9* BTDC, closes = 45* ABDC @ .050" = 234 degrees

Ehaust Cam measured @ .050" - opens = 40* BBDC, closes = 12* ATDC @ .050" =232 degrees

Both cams measure a total actual lift of .360" lift, that part surprised me. =9.144mm



the recognized improvements in this cam were to advance the intake a little more and retard the outlet slightly ...to gain more bottom end power (big car little motor ) from memory (better check my references though )

the lift was kept at 8.6mm because they made an interference type motor ,,,even had valve releifs in the pistons but i do remember there were a couple of cam profiles that aproached 9.1 mm lift

im guessing that all the engineers of this period must have been looking at the ford racing engines of the period and designing off their platform ...betya the shims are exactly the same too .

fantastic work there ol mate ....many thanks ...yes you didnt mention the year of your motor ..?

Ooops sorry fellaz, I'm talking about my 1985 K-100.

Rick

To me these are amazing figures, I'm used to timing my Vincent IO 55* btdc, ( Mk 2 cams).

I'd never considered that the inlet would open so late on K's, injectors squirting instead of relying on suck I suppose.

I'm looking forward to your figures with the new chain, will there be a significant difference?

Keep us posted,
Paul.

Paul, in effect the cam timing on an injected motor most certainly does not need to cater to the same "signal" demands as a carburated motor.
I refer to the signal as the suction you talk about.

Most motors however will work better with a good amount of valve overlap timing.
When you can get both intake & exhaust valves open by the same amount (measured distance off the valve seat) at TDC, you get maximum signal.
Signal is good, fuel-injected or not.
Turbulence in the combustion chamber can also be minimized when the valves (in. & ex.) are off their respective seats by the same measure.

Adjusting the cam timing in my view is really all based on those simple details.


I'm still waiting for my new cam chain...

yes its an odd way of checking rick ....but thats the reference material that i have to hand ....i think its got more to do with the nose of the cams and some way of getting rid of the various tolerances of valve gap durring cold or warm measurements ..

Alright, I am done my little job, and although I never did actually modify the stock timing I did find the source of that annoying noise I originally mentioned.

The new cam chain was really only slightly "tighter" than the old one. On measure I saw .050" less in OAL.

The result was hardly any change in the cam timing numbers I originally posted.

As I said previously, I saw no need to change the OEM valve over-lap timing as I was quite pleased with the OEM settings.

The problem that I did find, and fix was the cam chain tensioner system.

As I noticed on disassembly, the cam chain seemed to be loose, in my view, all that slack could very well be the source of the noise I was searching for.

I took a good look at the system, and decided there was nowhere near enough pre-load tension on the chain.

There is a very small (weak) spring in the tensioner, as well as a poorly designed tiny little ratcheting set of teeth that it supposed to maintain the position of the sliding post that pushes up on the lower chain tensioner.

Well, the entire set-up is aneamic, and not strong enough to maintain chain tension at any & all engine rpm's & engine loading.

There is a little hole, which does allow some oil pressure into the little tensioner to help it maintain some tension pressure.

On throttle and off throttle causes different load paths through the chain, and on off throttle running I had a strange noise.

Well that noise is no more...gone!

What I did was added a some extra pre-load to the tensioner using a section of valve sping from a GSX-R 1100 engine.

I took a piece of that spring, cut it down to 10 mm in length, and fit it onto the little vertical pusher-post that maintains the tension on the chain.

With that extra spring pre-load, there is still some movement in the system, but it is minimized substantially.

The engine now basically has the same sound on acceleration as it does on deceleration, no Grrraaaattt... on decel....

That is all for now.



Rick

nice touch rick .....ill have to remember that ..meanwhile go searching for a bit of spring as per your post ...

luckilly one of our local members works in a suzuki service centre . + i have the cam chain and guides refurbish kit to start soon ...

i too have noticed this phenomenom ...and put it down to old age ....grin

thanks for the heads up ...im sure more than some of us will benefit from this little beauty of a tip

cheers

Ok, to be specific, the little cut-down piece of spring I used is one of the inner valve springs.
There are 2 per valve on that model GSX-R 1100, an inner which has a smaller diameter, and an outer larger diameter.
I tried a cut-down clutch spring, but it was too stiff.
The vintage of GSX-R I used was 1987-1991 air/oil cooled model.
Really you could substitute other offerings, but try not to go too stiff.
I had to use a small C-clamp to compress the newly fitted spring onto the OEM cam tensioner, as finger pressure alone was not enough.
With the C-clamp holding the compressed assembly together it was easy to re-install it into place, and tighten-up the 2 tensioner bolts.

It all probably sounds tricky but it isn't at all, and if mine was like that I am fairly certain there are others.

Rick

On a Dutch forum a modification was discussed whereby a ballbearing ball was fitted on top of the spring (might have been discussed here before?). This was to close of the bleed hole on top of the tensioner in order to prevent the pressure loss due to a eroded plastic strip of the spring blade that sits on top of it. Idea was to have the ball pushed down when the pressure in the tensioner was high enough. On the later tensioners BMW fitted a sort of cap on top of the spring for a similar purpose. I have now fitted a ball on top of the spring, hoping that the functionality and the added 'pre-compression' of the spring will give better effect. I futher drilled the supply hole a bit bigger, hoping that the bleed hole is now the only restriction. Will let you know how it works when running again (have the bike in bits for a paint job - thinking of early K1200 yellow) :cyclops: