Boingk's Kawasaki KV100 [Pheonix Rising]

[lachbeth1125]

Re: Boingk's Kawasaki KV100 [Seat & new tyre]

Hey Noink,
Looking great mate!

Whilst you are doing metalwork, howz about making a "dummy" piece to make the original tank look longer? maybe with some knee dents?

Keep it up mate.
Cheers Jase 8)

 

[lachbeth1125]

Re: Boingk's Kawasaki KV100 [Seat & new tyre]

Sorry bout the typo. :-[ B not N

Hey Noink,
Looking great mate!

Whilst you are doing metalwork, howz about making a "dummy" piece to make the original tank look longer? maybe with some knee dents?

Keep it up mate.
Cheers Jase 8)

 

[boingk]

Re: Boingk's Kawasaki KV100 [Seat painted + final mockup]

Torrential rain stopped and the sun came out this afternoon, so I thought it'd be a nice day to get the seat painted and fitted. The base sections were joined together with pop rivets and sanded down with 400 grit paper. After a quick rub-down they were sprayed green to match the rest of the bike. It is a compression fit for the moment, with the whole shebang held on by the side tabs on the seat section.

I've figured the final position for the pipe, which should see the silencer exiting to the left of the rear cowl and fairly level with its line. I'm happy with how it all looks, so am going to try and bring the lot together. Padding for the seat will be self-adhesive neoprene (if I can find it).

All thats left to do is wire her up and weld the silencer onto a stock collar ready for mounting. Indicator lamps are going to have to be wired on a seperate system as I can't find a diagram and all previous attemps have failed. Ditto the headlight and horn. It should be fairly straight forward. Famous last words perhaps?

Cheers - boingk

 

[Big R]

Re: Boingk's Kawasaki KV100 [Seat painted + final mockup]

Pardon my ignorance about OZ, but can you find a foam hunting seat? I don't know if you saw it in my thread, but that's what I'm using.

 

[mikeadamstattoo]

Re: Boingk's Kawasaki KV100 [Seat painted + final mockup]

looking awesome man! i always see old two stroke dirtbikes/enduros on craigslist and wonder if theyd make cool cafe style racers, i think im gonna need to pick one up for cheap and do it to it!

 

[boingk]

Re: Boingk's Kawasaki KV100 [Seat painted + final mockup]

I've got no idea what a foam hunting seat is, sorry Big R. I do like the look of the seat in your 175 thread though, very slick indeed. Meanwhile, I'm just attaching layers of EVA foam to the seatpan with waterproof contact cement. The reason I made up a seat from scratch is nothing was around locally and I had the materials. That, and the stock one was cactus.

Thanks Mike, and I gotta say your 550 came up looking pretty champion. As for the stroker project, thats the spirit! Big things to look out for are the suspension, axles, rims and sprockets. If its been abused (as mine was) then you may be up for new items (as I was). A big plus is that chambers and carbies are cheap and plentiful, especially if you research your options and are willing to do a few simple mods.

Cheers - boingk

 

[boingk]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

Ok, so I was on a flag point this Sunday just gone out at the local track. It was for the Post Classica Racing Association, and I saw everything from home-brewed hot-shot CB125's to rip-roaring Ducati's and CB750's. Even got some sidecars in for a hoon around. Brilliant stuff.

The upshot of it is that I'm now determined to scrounge funds and build a race bike for the Post Classic ('63 - '72) 125cc class, also running in the Superlite class; air-cooled 2T up to 111cc and aircooled 4T's up to 159cc. The action out on the track between the tiddlers was awesome, and the corner speeds were actually pretty impressive.

So heres my list of essential modifications to the KV100 for racing:

Port the cylinder (3mm wider & 1mm higher on exhaust)
Cut rotary disc (30~40 degree longer intake cycle)
Enlarge carburettor venturi from 19mm to ~25mm.
Refill shocks with heavy-weight oil, renew seals.
New rear tube & tyre.
Fit RM80 expansion chamber.
Strip uneccessary conrols & oil injection.
Strip right-side engine cover.
Strip kickstart, guards & lights.
Remove battery & unesseccary frame tabs.

Should lighten it up a bit. Oh, and this came in the mail today...wonder what I can use it for?

Cheers guys - boingk

 

[beater]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

it sounds like it, but did you do the math on the crank cutting? usually your looking at around 3:1 intake vs exhaust on piston ports for the crank cut back. Make sure your cut is angled as well, and not oblique/right angled.

But you knew that already didn't you... lol

I have some 2-stroke design software if you hit me with your email or pm, I should be able to get it to you. It's a java based deal. You can caliper your rm 80 and see how it compares. You will need some stuff like port angle and length, but you'll know that stuff...

I raced an rd400 in the day, and I have 3 smokers now, albeit they're all scooters/mopeds... I almost think piston ports are easier to tune than reeds. How many ports does this beast have? 3, 4 or 5?

 

[boingk]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

Cheers for the inquiry, beater, and yeah I reckon I know what I'm doing. I've put a fair bit of time into researching what needs to be done and how. Essentially I'll be copying the tuning specifications of the G31M 'Green Streak' racer of 1970's fame. Found them online and am using them as a template for this - the Kawasaki manual actually gives 'Speed Tuning' instructions!

Not sure how many ports this fellow has, but I think its 4. One exhaust, one main intake and 2 transfer. Timing is detailed on the previous page or two somewhere, along with my pipe calculations. I should get a relatively potent powerband, but with decent duration as well. Good combination, but thats all theory. The real test will be getting it out on the track and letting it rip!

I've detailed the software I used in the 'Smoking Lounge' thread up top of the Cafe build board, check it out. Not planning on cutting the crank or anything big internal (other than porting the cylinder) but will simply remove the disc assembly and recut it on a bench with my Dremel to allow a 210' intake duration from 140' BTDC until 70' ATDC.

Cheers - boingk

 

[boingk]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

Progress report:

Dewired the bike. Everything has been stripped, including the ignition barrel and main wiring loom. The only wires remaining are those inside the magneto, and the one that takes current from it to the coil. I'm planning to patch the handlebar kill-switch into this setup so I can stop the bike by grounding the circuit out. Spark is provided by an NGK B8HS, one stage cooler than stock.

Fitted #32 rear sprocket (previous was a #42) and drilled the rear brake drum. Also fitted a new tyre to the rear, same as the front (Kenda 3" x 18"). Should run alright, all I need to find out is a chain! The 'P' plates are there to give an idea of where the racing numbers will need to go.

Bought what is touted as the 'hot-shot' item for Superlite racing - a Honda CR80 expansion pipe. This thing looks all kinds of evil, but I'll have to see how it fits. If it needs major modification or is massive overkill (too many revs needed to work), I'll revert to my original plan of using the RM80 pipe I prepared earlier.

Still waiting on rebuilding the forks with new seals and 20 weight oil, but that shouldn't be too much hassle. The caburettor, on the other hand, may be more of a challenge. Its either bore the original to 25mm, or bodge the 25mm one I have onto the intake...somehow...

Cheers - boingk

 

[Big R]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

This things lookin good Boingk. Any luck on that CR80 pipe yet?

 

[boingk]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

No luck on the pipe, gonna test the RM80 one first, but big smiles on the test run 8)

I pushed it a few kay to a cycle shop I deal with a bit, and they fitted an O-ring chain on the spot for me. I pushed it out of sight of the main road and fired her up, took a seat on the frame rails and let her rip along some quite roads close to home. Saw a good 70km/h without pushing very hard at all on the throttle or the gears and it pulls well from a standing start - I'd say the gearing is spot on for the track.

Ran the 15/32 sprocket combo through a gearing calculator and came up with a theoretical top whack of about 145km/h which seems about right after the road test...although having the power to get there is another thing. The handling is top-notch and stopping isn't too bad, although I'll need to rough the front shoes up a bit as they felt (and looked) a bit glazed.

More pics and a potential video coming as things develop.

Cheers - boingk

 

[boingk]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

Was up in the shed over the weekend and took a crash course in arc welding. After attaching 50mm of the KV100 manifold to the CR80 expansion chamber, heres the result:

The Honda CR80 pipe seems to work quite well, although the revs are being restricted something shocking at the moment by the stock carburettor. Testing was offroad out at the farm with a few mates who put me to shame on their competition bred 450cc dirtbikes; had a grand old time of it with some beers and a bonfire afterwards. The performance is much better than standard, and I'm anticipating an even better top end after I fit this:

Thats a Keihin PE28, the largest allowable two-stroke carburettor in the Superlite racing division. Its from a local race shop and the jetting should be fairly close as it was on a Moriwaki 80cc stroker. I may have to change to a 34 or even a 36 tooth rear sprocket after testing - I need a top speed of over 75mph to be anywhere near competetive, but at the same time I only need to hold that down the last few seconds of the straight otherwise acceleration will be compromised too much out of the turns.

Cheers - boingk

 

[GroovyAardvark]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

Awesome build mate, so funny we are essentially doing the same thing!
I think I'll need to get all of my racing advice from you. Certainly looks like you know a hell of a lot more than me in that department!

I was just talking about those strange looking 2 stroke racing pipes the other day. They look soooooo weird but I would be curious to hear from you how much of a difference they make?

Cheers,

Leigh

 

[boingk]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

Yeah I've been researching and fiddling... its kinda what I do. And yeah, worlds apart but the same idea - gold!

The 'strange looking' pipes are really finely tuned exhausts that utilise the reflection of soundwaves to boost the power of the engine. In laymans terms, they're a sort of turbocharger for two-strokes. If you want the short answer, read the last line before I sign off.

The long neck that slowly tapers wider in diameter helps provide a fast, clean getaway for the exhuast gasses. They are extracted cleanly by it and this improves the efficiency of the engine by leaving relatively few spent gasses behind. Some fuel/air mix if pulled through as well, but we'll deal with that later.

The next section, where it stays roughly the same (fairly large) diameter, is called the dwell. This is merely a joining section between the extraction cone and the next section, but its length is important because it helps tune the power characteristics.

The part where it tapers down is where the exhaust pulses reflect back towards the exhaust port. The sharpness of the taper governs how big the powerband is, as well as its duration. Long, narrow taper gives less power for longer while a sharp, short taper gives more power for less time.

The last section, the 'stinger', governs how fast the pressure in the pipe bleeds down, and is crucial for controlling the movement of exhaust pulses within the pipe.

So, remember back at the scavenging horn? How the spent gasses get extracted and some air-fuel mix makes it through too? Well, the reflected shockwave from the tapering-down of the pipe rams this extra 'wasted' intake charge back into the already full cylinder just as the piston shuts off the exhaust port. This has the effect of 'turbocharging' the engine; ramming more intake charge into the combustion chamber than would be normally possible.

For example, a well tuned 100cc four-stroke may combust 110cc worth of intake charge at its power peak. A well tuned 100cc two-stroke may combust upwards of 180cc worth of intake charge at its power peak! So...why do you have to rev the hell out of them?

Generally speaking, the pipes are tuned to work at certain engine revolutions. This is because the reflected waves from the end-taper of the pipe will only reach the exhaust port when then piston is in the right position at the revolutions the pipe is tuned for, thus 'turbocharging' the engine and maximising power over a certain rev-range only. This is often at the upper-end of the rev-range, as more strokes per minute equals more power output to the rear wheel.

When designing a pipe from scratch you can finely design and manufacture it to give your bike any characteristics you want - lots of boost up high; a good, usable spread of power from the midrange upwards; minor boost everywhere. In the racing world you're chasing the former - lots of boost in the high-mid and top rev range. Combined with proper cylinder porting, ignition timing and carburettion you'll be maximising the possible power out of your engine.

However, making pipes is expensive for the average joe, and we generally lack the equipment and manufacturing expertise to make them...even if we did somehow design a good one with the aid of our computer. So...what now?

Answer: we cannibalise other bikes exhausts! I'm trialing a Honda CR80 pipe and it seems alright. I'll see what an ignition advance and larger carburettor do to improve things. If it doesn't work, I'll go to the RM80 pipe. Easy really.

So, thats the theory behind expansion pipes. The special shape allows the exhaust pulse to be reflected back towards the exhaust port, and this reflected pulse rams intake charge that has bypassed the combustion chamber back in, thereby allowing a larger volume to combust than is otherwise normal. Hence, more power.

Cheers - boingk

 

[brainrush]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

I'm really interested in seeing what that monster carb can do!

 

[alpinaclone]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

I like the direction that this is going.

I would find a bigger drum for the front of that thing. I don't thing the stocker will last too long before fading under racing conditions at 70+mph.

 

[boingk]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

brainrush - yeah, so am I ;D

As for the front brake...I'm looking for a rim with the same dimensions that has a TLS setup on it. That way I can swap the brand new tyre and tube straight over. Until then, it'll get some holes drilled in it but thats about all.

Cheers - boingk

 

[boingk]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

Through the haze, the machine stood ready. No mention was made of its crudeness, for it would surely be effective. Designed by a lunatic and ridden by a madman, this diminutive machine was the last bastion of days gone by; of the shrill wail and pungent haze that used to be synonomous with motorcycle racing. This was...

...the last Two Stroke.

I've wired the handlebar kill-switch and am ready to mount the seat. After that all that needs doing is affixing racing numbers (cutting up plastic buckets and applying stickers) and cleaning it up ready for scrutineering. Probably need to give the frame a going over with degreaser and 2000 grit paper, and the spokes a similar treatment plus silver paint so they look the goods.

The 28mm Keihin makes a huge improvement. Its mounted using a piece of radiator hosing and two hose clamps - very, very simple stuff, but it works well enough. I'm very tempted to road register this in my earlier 1972 frame, which would make for easier registration and no need for turn signals. Be an awesome town run around, especially once I get a longer tank and some signwriting on it. Theres a local business interested in making a seat for it, too.

That 'last two stroke' comment was just because I got my category papers...and I'm the only stroker on the grid! Its me versus about a dozen modified CB125's and a lone Suzuki GS125. Should be interesting.

Cheers - boingk.

 

[Big R]

Re: Boingk's Kawasaki KV100 [Caught the race bug...]

Can't wait to see this one all buttoned up. The anticipation is killin me!

By chance, did you see the plastic tank that Curbcast got for his moped?