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Old 23rd June 2017, 11:10   #31
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Default Re: Revived, rough & ready: Kawasaki KB125 RTZ Junkyard Dog

Sadly Bajaj didn't retain the resonator box in the 125. I had one retro fitted and that required a change of the Rhs engine case...not the crankcase but the one before on which the carburetor is mounted.
The disc valve had splines which made it sit in the correct slot behind the carburetor. I had ported that setup slightly to improve airflow and remove casting defects from the area
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Old 27th June 2017, 21:40   #32
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Default Re: Revived, rough & ready: Kawasaki KB125 RTZ Junkyard Dog

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Originally Posted by Crankpin View Post
Your bike's tank has the mounting for the " Intake resonator". The KB125 didn't have those and they came on the earlier 100s. So you could also try installing the KB100s Power-Box/ intake resonator box onto this. I had one installed on my KB125 back then and it did make a significant difference on the initial and mid-range rpms. You'll have to grind a bit of the last 2-3 fins on the RHS side of the block.

Also, you'll have to get an older KB100s RHS crankcase to be able to fit it as that came with the nozzle to attach the resonator hose onto...bit of a headache to find now I guess.

I remember I had modified my bike's clutch as well...the 125 came with the 100s clutch plates and clutch basket so wasn't too effective to handle the extra 25cc power...can't remember what exactly though!
Thanks... I still have a '92 KB100RTZ - mostly in pieces - Mangalore registered in name of orig. owner, a friend - that's where the tank came from. I still have the engine cases and everything else - just not sure I'm ready to part the bike out yet; it had a character all its own; less vibes and much freer-revving than the 125 (which is mostly low-midrange grunty and thus IMO doesn't require the intake apparatus). Anyway used the 100cc tank in favor of the 125's because it was earlier modified and I liked the taller look... also liked the screw-on K-Bajaj (or Kawasaki) logos; and lastly, my 125 tank got badly dented in a little rider training session gone awry (my buddy fared worse - a broken leg sadly)...

I've got the the five-plate clutch setup from the Caliber 115. Still slips till nicely warmed up, but I'm pretty sure that could be resolved by running 4T (friction additives) and by replacing the stock springs with stiffer ones from whichever spring-wallah down at Ajmeri Gate...

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Originally Posted by ashwinprakas View Post
From purely a function over form POV it would be better if you could scrap those fancy plain mirror RVM's and go for a decent pair of purpose built RVM's. My personal favorite is the RTR RVM's the view is just commendable.
I'll look into those, thanks... these are admittedly of rather limited effectiveness... though I confess that for years I ran with no mirrors at all and only miss them a little bit when they're gone entirely. These are better than nothing, to be sure.

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Originally Posted by Suresh Stephen View Post
Eric, Your bike looks nice. One doubt, The induction resonator came in the next model is it. Also are you based in Manali?. I will be touching Manali on next friday after Pangi valley drive
Re the resonator see above... and yes, a bit north of Manali. Would be great to meet up. Tried PM'ing you my contact info but it wouldn't go through. Is your box full? Maybe you can try PM'ing me your e-mail/phone?

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Originally Posted by vrprabhu View Post
The round headlamp and circular instruments do look better than the original rectangular set-up. Now, if you could only find a way to incorporate 'Kawasaki' monogram (which the original bike had on its instrument pad), it would be a tribute to its origin

Just my two cents on the latter part of your post -

a. KB had a rotary (intake) disc. Getting the timing right was a skill. If you get it right, it had one of the best pickups. Loose it, then it was all smoke and no fire!

b. The accelerator cable used to be split into two - one for the cable and the other for the oil pump. I can see that you have retained the set up - from the pictures. In my experience, the quality of 2T oil is critical for its performance. Preferred to Gulf to Castrol. Later on switched to ELF - don't know what is available in the market now.

c. Similarly, the engine oil. The result of these two will get reflected in the exhaust and the spark plug.

d. The exhaust itself needs its own care - workshops used to wrap steel wool on the inner (perforated) pipe which was then inserted into the silencer. One can easily make out when it needs cleaning from the exhaust (growling) sound. (I hate the closed units of today's 4 strokers).

e. After the first re-bore (while approaching 1,00,000 kms), switched over to Mahle piston kit. There was one more available - 'Usha'? My mechanic swore by them (especially, as Yamaha rode on (escorts) Mahle). The pick up was definitely better.

f. Finally, the chain and sprocket kit - bajaj replacement kits weren't up to the mark. I used TI Diamond (racing) Chain kit, which was much better.

I had owned KB100 from 1988 to 2004. An experience which I will always cherish......

The original KB100 (the monogram of which eric has used in the side panel) -
- was followed by KB100 RTZ (the monogram of which is on the petrol tank - the original had 'Kawasaki' as opposed 'K-bajaj') -
- which was then given an 'upgrade' to KB100 RTZ DELTA Super Tuned Engine (when the 'Resonator' box was introduced) -
- and was retained in 'KB125' if I am not mistaken.....
Ahhh... thanks, this solves the mystery of the side-cover monogram... original KB100... need to find another of those. Or else the SE-Asian-market gold GTO badges, which also look nice IMO.

Revived, rough & ready: Kawasaki KB125 RTZ Junkyard Dog-gto-side-covers.jpg

Might pick up some original Kawasaki tank badges, which should screw-in directly in place of the K-Bajaj pieces and were probably used on a bunch of other Kawi's of the era besides.

Re: the rest, thanks for sharing your experiences.

a) AFAIK (I've personally rebuilt both the 100 and 125 at least twice each), the only skill required in getting the rotary disc timed is the skill of not putting it in upside-down - there is no adjustability per se, a dowel pin positively locates the assembly radially on the crankshaft. Unless you're talking about grinding the leading/trailing edges to alter the basic port timing, for hyper-performance applications. Which of course would take a fair amount of skill / trial-and-error.

b) Striving for even more minimalism, I actually removed the 2T injection pump on my 100 and ran pre-mix and a standard single throttle cable from whichever generic Platina/Boxer/Caliber (solves the trouble of sourcing special cables, and there's no chance of the pump cable breaking or pump failing and starving the engine of 2T). I retained the pump on the 125 for convenience sake, and with it adjusted right get very little smoke after the first couple minutes from a cold-start. I've not noticed any performance difference with different brands of oils - I guess I've run about everything... of course, I'm not drag racing. The bike just always runs strong enough to put a smile on my face (all that's required).

c) ??? Relationship between trans/clutch oil (no engine lubrication outside of 2T actually) and plug/silencer??? There is no means of communication between one and the other. Did I misunderstand?

d) The real pain is in getting the core out when 1) it's full of carbon; and 2) the silencer's dented as deeply as mine is - since the baffles are the same diameter as the silencer's OD (I drive the core out with a 1/2" GI pipe from the front end, but that ain't pretty to watch). I really wouldn't mind a tuned expansion chamber. Used to be a lot of them around here on old RX's but haven't seen one in awhile now. Kaulson used to make a midrange-specific model. Anyone have a lead?

e) I've got a Mahle in it, too. Good international company. They used to have plenty of these in stock down in Karol Bagh but in the last few years the sellers have been scrapping old stock - just taking up too much space on the shelves I guess.

f) Since my swingarm is extended, the stock chain is the wrong length anyway. The o-ring type original model Discover 135 was just the right number of links (and beefier), but those aren't easy to find now either, so I just get Pulsar chains and cut them down a bit as needed.


Quote:
Originally Posted by Crankpin View Post
Sadly Bajaj didn't retain the resonator box in the 125. I had one retro fitted and that required a change of the Rhs engine case...not the crankcase but the one before on which the carburetor is mounted.
The disc valve had splines which made it sit in the correct slot behind the carburetor. I had ported that setup slightly to improve airflow and remove casting defects from the area
Thanks... I ported one of my carb-mounts but without other corresponding changes, didn't notice any positive effect. I've thought of fooling with the disc a bit in terms of increasing port duration (more top end) by grinding off the leading/trailing edges a bit... but it's all a little experimental unless you've got some very clear specs to work with or know someone who's succeeded at getting a bike tuned the way you'd like it, too. As for me, I get the jetting right and keep the silencer / air filter clean and it runs pretty much how I want it to. All the time.

Thanks, guys, for all your inputs. I see this thread is bringing back fond memories for at least a few...

-Eric
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Old 1st July 2017, 18:12   #33
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Default Re: Revived, rough & ready: Kawasaki KB125 RTZ Junkyard Dog

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Originally Posted by ringoism View Post
a) Unless you're talking about grinding the leading/trailing edges to alter the basic port timing, for hyper-performance applications. Which of course would take a fair amount of skill / trial-and-error.

c) ??? Relationship between trans/clutch oil (no engine lubrication outside of 2T actually) and plug/silencer??? There is no means of communication between one and the other. Did I misunderstand?
a) Exactly that is what I meant - since the carb sits inside, there wasn't much scope to tinker around with a bigger one; the bigger port and timing was the other alternative to see how much performance can be increased.

c) My bad. What I meant was - at every servicing to change the engine oil, I used to get the silencer cleaned. The silencer code will be wrapped up in the cotton wool AFTER dipping it into the engine oil. No idea why my mechanic used to do it - probably to prevent any rust or to ensure that it doesn't go up in flames? (I have seen fire coming out of the exhaust of RX100s / Shoguns). But there is another small (miniscule) source for engine lubrication - the PU air filter element was recommended to dipped in a 'heavy' oil, which may get sucked into the intake You have opted for a 'free flow' open air filter, where the filter is bound to have some element of oil in its membranes - depending on the fabric used?

As far as the timing goes, Bajaj Dealers used to have a machine to read and synchronise the timings (you may find it the user manual) - or was it the workshop manual?
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Old 10th August 2017, 09:52   #34
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Default Re: Revived, rough & ready: Kawasaki KB125 RTZ Junkyard Dog

Quote:
Originally Posted by ringoism View Post
a) AFAIK (I've personally rebuilt both the 100 and 125 at least twice each), the only skill required in getting the rotary disc timed is the skill of not putting it in upside-down - there is no adjustability per se, a dowel pin positively locates the assembly radially on the crankshaft. Unless you're talking about grinding the leading/trailing edges to alter the basic port timing, for hyper-performance applications. Which of course would take a fair amount of skill / trial-and-error.

-Eric
Quote:
Originally Posted by vrprabhu View Post
a) Exactly that is what I meant - since the carb sits inside, there wasn't much scope to tinker around with a bigger one; the bigger port and timing was the other alternative to see how much performance can be increased.
I have done the same in the late 1980's Bajaj Chetak which I got from my father. I had the scoot with me between 1999 and 2002. The Bajaj/Vespa engine use the same rotary induction but instead of using a disc does the induction timing (opening and closing of the gate into the crankcase) by means of the crank web itself. I cut the crank web 5mm backwards to increase the intake duration. The cut could have been slightly larger but with limited fuel money available then I did not want to risk the fuel efficiency. The disc should fully close when piston is at TDC and before it started its trip back to BDC to prevent mixture blowing out back.


Before the rotary intake mod I had previously increased the exhaust port duration and skimmed the head. That combined with the rotary mod the scoot was too much fun to ride and had good high RPM performance to keep up with my friends' stock RX and KB125. With a properly made expansion chamber which was available from UK/Italy the scoot could have easily become faster but was out of my budget!

During my high school days KB 100 was my benchmark in motorcycles available at that time. 12volt electrics, bright headlight, parking light when vehicle is locked, long wheelbase, long travel front shocks, comprehensive meter console with tachometer etc etc.
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