XJ500T Jaybuilt Kawasaki 500 Bellytank Triple
XJ500T Jaybuilt Kawasaki 500 Bellytank Triple
Jaybuilt XJ500T Kawasaki Bellytank Triple
Builders of incredible homebuilt machines keep popping up andhere's another example of a very impressive motorcycle designed forthe purpose of handling the twisty roads of California's canyons.This bike consists of a Kawasaki 500cc 2 stroke triple engine,front and rear suspension from a ZX9 and everything else”Jaybuilt.” Total weight is 310 pounds!
Jaybuilt XJ500T Kawasaki Bellytank Triple
Thewhole project was really well thought out. His intention was aminimal part count and easy maintenance, engine swaps are under 30minutes. He built an engine stand that holds the engine with 1 boltand slides under the bike. Remove a few bolts, disconnect a fewwires and hoses and slide bike away, the engine is on the stand.The entire bike can be disassembled with about 20 bolts in under anhour.
Jaybuilt XJ500T Kawasaki Bellytank Triple
Thefuel is carried in the foam filled bellytank, the area over theengine encloses the expansion chambers. He says heatwrap anddirected airflow keeps everything cool.
Jaybuilt XJ500T expansion chamber routing
Performance, as you might expect, gets your attention. He gearedthe bike for a top speed of only 120, he figures he wouldn't beriding anywhere at 160 so why not keep the power where you can useit.
Jaybuilt XJ500T Kawasaki Bellytank Triple
There's a lot of interest in 2 strokes among builders of back roadspecials. I can only imagine what this bike is like to ride, lotsof grins for sure. The readers over at the Bay Area Riders Forum,where the builder talks about it, all seem to like it, a lot, and Ihave to agree with them, this is one superb build.
Bigtip of the hat to Andy, who pointed this out. Thanks!
Link: BayArea Riders Forum
Jaybuilt XJ500T Kawasaki Bellytank Triple
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Lovely to look at and nicely crafted, but I don’t understand thelogic of flipping fuel and exhaust position from what’s “normal.”The builder has the hot stuff where it impedes flow to thecylinders and heads and pretty much ensures he’ll get baked atevery stop. The fuel, down where road debris and obstructions coulddamage the tank, must be pumped up to the carbs. But again, it’s agreat looking special.
Heat isn’t an issue if you’re always flying!
I love the exhaust routing, a bit crazy, but still awesome!
I can say I would be a bit nervous having my gas tank nearlykissing the ground, but overall I think this bike is beautiful.Loving all the custom builds kneeslider
Very nice build and shows some radical problem solving skills, lovethe idea of using that motor in a modern frame, the next step mightbe to reverse the cylinders and route the chambers straight out theback
The purpose of the tank on the bottom is weight distribution. Byhaving the center of gravity so low this should be ratherflickable. I do agree with the danger to the tank from FOD, but theexhaust heat would not be much of a problem with thought taken forinsulation and routing. I like the idea.
There are many different and unique design features on this bike! Ithink the best is that of the quick removable motor. Have a littletoo much fun and cause some engine damage, just bolt it down andremove it to do the work and the engine stand you already own.Great concept for the tinkerers who are always looking for somemore power between dyno runs or races.
Considering where radiators, oil sumps, etc are positioned, I findit hard to believe there is any real danger with placing the tankbelow the engine.
I find it both funny and absurd that having several gallons of gasbetween your legs is somehow desirable or safe. Yet nobody FUDsthat design convention.
Is this a street bike or track weapon? No matter – I love seeingwork like this.
That’s a nice piece of great mechanic …. I really like the idea ofthe old school 2 stroke powerplant fitted with modern suspensionand an effort to reduce the weight.
The esthetics is discutable, but that would be a blast to ride …damn !
routing the chambers directly out the back probably would notprovide enough exhaust chamber space without changing the look andchanging the weight centralization.
Now that’s really cool! I love the Kawasaki triples. I’d like tosee one with an old KZ motor, reversing the head so the carbs arein front and the exhaust goes out the back. The belly tank shouldimprove the center of gravity for better handling. My complementsto the builder for a great design. Keep up the great work.
Sweet design, I like how there are blatant criticisms to theplacement of that exhaust as to the daily performance of themachine. Gotta understand it’s performance built and moving crazyfast will maintain heat and he only geared it for a top speed of120, talk about form and function.
It does look like the builder (artist?) reinforced the belly tankwith an additional plate at the front and bottom. I would like tosee how the weight of the fuel and tank compares with the weight ofthe exhaust system. In any case, my applause for great creativityand build skills. The original triples were infamous for diceyhandling. This should be far better.
If I remember right, a number of TZ700/750s were built (by thetuners?) with the middle 2 cylinder exhaust ports directed aft.
I let me state up front that I think the bike beautuful, but if I’mremembering correctly, when Honda set up Freddy Spencer GP500 racerlike this homebuilt, they had real problems. Maybe because of thevolume of gas that they were trying to carry, but as the bike wentinto the corner, the fuel would be swinging out. It made the bikevery unstable. They also had heat issues with the exhaust system. Ithink it only lasted 2 races, before they switched the bike back tothe normal setup. he may not be running the engine anywhere as leanas the race bike would have run, and hense, not have the heatissue. Regardless, when most of the US just watch’s TV all day,it’s really neat to see someone push the envelope, nicework.
Lowering the center of gravity is not always desirable. When amotorcycle leans into a turn, it rotates around its’ center ofmass. The center of mass of the entire bike, including the rider.This is why mass centralization is such a hot term these days. Butwith such a light bike and being so short top to bottom, I don’tthink the builder will have any problems with flickability.
Anyone else notice the switch to single front disk in the finalform? I wonder if the dual disks had too much braking for such alight bike.
I like what he is doing and am glad to see something truly customin mail order custom world
What an incredible project. I’ve had enough fuss just making abelly pan and number plate brackets.
Great job on the design too; is there an opportunity to sell a kithere, sans motor?
Jay, nice work bud. That bike is in a class of it’s own!
Interesting design. I bet the road in CA are a lot nicer, I wouldrip my tank off in 10 minutes with how crappy PA roads are.
I really like the whole design concept of this bike. Minimal partcount, accessibility, mechanic friendly, and fast. I’m not sure Ibelieve it’s just 20 bolts holding that whole thing together butI’m sure it’s not much more than that. I think it would beinteresting to leave the expansion chambers and frame exposed, butthe heat would probably be quite uncomfortable for the rider. Verycreative and excellent end product. Very nice.
Is the fuel pumped up through the fuel cap?
My dad had a five hundred triple, he called it the widow maker, theengine ended up in a rickman frame. I used to like two stroke in mygo fast days but have been a bit turned off lately when I heard howmuch air pollution they put out.
Great bike, really well thought out,it sounds like it is supposedto go on the road, will licensing be an issue in CA(pollution)?
I never said it wasn’t done or couldn’t be done. I mentioned that,if it was done, it would change the look and possiblycentralization of weight.
aaron weltonIII says
absolutely superb congrats
he knew what he wanted and got it done
and beautifully so
Understood. Someone explaned the reasons for the TZ cylinderre-orientation – it made sense and I’ve since forgotten what theywere.
This all makes me wonder what his H2 project (if I read the forumlink right) will look like…….
P. T.Anderson says
I like the way this chassis layout allows for experimentation. If Isquint just right, I can imagine the tank and pipes in theirconventional locations with or without the cylinders reversed.There’s room in there to try stuff out without altering the frame.I could comment more but it would sound like I’m being a downerwhen I didn’t mean to be so I’ll just leave it with a very earnest– Looks like it will be a lot of fun!
if I see this motorcycle I’m remember my cycle kawasaki GTO110ccvery small i like your cycle but i see your body cycle veryinflexible in some point.
Anyone that criticizes the looks should take a second look at therear view, those three pipes sticking out look awesome to me, andsubtly scream how different this bike is.
Sure there are other triples, but they are a rarity on theroad.
The workmanship looks top notch to boot.
hi there boys it looks like most of you like it.I apreicate all theopinion’s and thank you guy’s for taking your time to reply .
JAYBUILT OF LOS GATOS CA
As an English man from the lake district which is a ruralmountainous area I have to say that would be a superb bike for theroad conditions round here. With the gearing that it has it alsoseems it would be perfect for tarmac hill climbs likebarbon.
The bike looks GREAT and the design features make it quite uniquebut in looking at it it’s the exhaust system that stands out as atrue engineering feat, getting it where it is is one thing butmakeing it work is quite another, 2 strokes are VERY touchy when itcome to there exhaust design, everything has to be just right or atleast Damm close or they will have flat spots on the low end andjust plain won’t run good at the top end, my hat is off to thisguy.
I love this bike. It’s super light and likely extremely powerful.Despite what some have said about the high exhaust, the overalllayout of the bike seems pretty elegant to me.
Nice work Jay! Props to you for the killer build
So what is stopping major manufacturers from building reallyelegant, simple framed bikes like this?
I want this bike with a huge single cylinder 4 stroke!
Become the manufacturer and build it yourself. What is stoppingyou?
Yeah Honda did this with the NS500…fuel underneath exhaust chambersup top. Cool bike. Not too crazy about the white colored parts.
one thing that interests me is that its referred to as a “backroads special” implying use on the street, but it has zeroconcession to making it road legal that I can see: no lights, noindicators, no licence plate etc etc. The extra frisson ofadrenaline when seeing a cop must make an already exciting rideeven more exciting…
I remember reading a tech article about Spencer’s NS500 with thisarrangement. The term used was “polar moment of inertia” IIRC:basically as the tank empties, it drains away from the center ofmass. Although the total mass gets smaller (as the fuel is used) itacts further away from the centre of mass which caused slow turnin, and understeer. Hopefully I am not greivously misrememberingKevin Cameron.
I guess the only way to test it would be to ride it, which I wouldLOVE to do…….
makes my own projects seem kind of lame, seeing this stuff.
Hi all !! the lights are the one thing that i cant make myself…….yet ! and they can make or brake the looks of it so i am foolinwith some military stuff at this time nothing I am OK with yet. butit will happen . i am trying to build a hud system for the helmetwith rpm ,mph,high beam ,blinker,and kill switch when unplugged.just walk up and plug in and go ! thanks jaybuilt
Sticker Boy says
Great looking bike! As for the gas tank, I wouldn’t fancy mychances riding it in the pot-hole center of the universe where Ilive. Crack it on the side of a pot-hole and… I wish they’d fix thegoddam roads!
I’m in the planning stages of an air cooled 650 based cruiser, noreason the same inexpensive motor couldn’t be used on a sport bikechassis.
Their are plenty of Honda and Suzuki motors like this outthere.
I have no intent of making it a business, I just want ONE.
very good looking bike. i can’t wait to see it with lights andsuch. the roads in my area aren’t to terrible so the belly tankdoesn’t concern me to much. although i would be worried about mytwins with those pipes running right underneath them. that must getHOT!
With the lower center of gravity it should be easy to changeorientation, but what about lean angles? In order to sustainmomentum through a corner do you have to use more body positionchange than a typical sport bike with a higher center of gavity? Imay be incorrect in my thought processes on moment arms androtations so I hope you can enlighten me.
43 comments so far ..that’s what its all about. Jay builds thingslike this because he can its a passion (the artist thing) I’m surehe has enjoyed every moment of construction and constantly thinksof changes or “next time I’m gunna “
MichaelLackey (aka BykDr) says
The design that he used seems sensible, I built a H-1 drag bikeback in the eighties and one of the main issues was instabilitycaused by engine vibration…his designs has the forward enginemounts come directly off the head. That should minimize thatissue.
I see a lot of talk about his fuel tank location he might haveimproved it by designing a tank that was below the seat and rightbehind the carbs…thus allowing the greater mass of the engine to bemounted lower…and possibly building a airbox as a part of the tankdesign.
An airbox would allow a large dead airspace which tends to give abit better low end response.
As to having the expansion chambers routed upward…two strokeengines are not real fuel efficient and the exhaust tends to rundfairly cool as compared to a four stroke. I have ridden many offroad two stroke bikes with up exhausts with no issues. His designreally approaches the old Tz 750 design.
Does anyone see a possible wheel jamming between the pipes on forkcompression like I do ? YIKES !
Jay, Pariah here from customfighters. Nice to see you getting theexposure the bike deserves.
thanks SEAN nice thing to say and all of you customfighters are aclass act.
Very very cool. Nice paint too = )
Absolutely stunning use of one of the more interesting engines. Itmakes me happy that people are building such creative, inspiring,and FAST machines! I want to hear this thing hook up in a cornerand wind out the line.
thanks Adam we will have to get togather and you can ride it betteryet .
i would move the gas tank to the rear fairings and have it blend inas if it was part of the plastics other than that thats a hotbike!
GUs THeBUs says
The Reason for the exhaust is that it is 2 stroke meaning it takes2 strokes to make one power stroke un like most things which are 4stroke the exhaust buldges are the expansion chambers When theexhaust comes through the small part of the begining tube it thengoes into al larger tube and is then slowed down by the shrinkingtube at the end of the expansion chamber and when the stroke startsover and intake starts it sucks back all of the hot oil and gasthat has not been burnt or exhausted through the end of the tubealready and because the gas is already warm it combusts at a higherrate creating more horse power
Watch out, one of the big 3 will probably copy your ideas like theydid with someones single rear shock idea 20 years ago.
If Kawasaki would have built this bike in 69, a lot of bikers wouldhave been able to keep thier 500 on the road.
thanks for the warning scott but it has ben done by honda back inthe 80`s and did not do well . I shure like it and I am going to doa 750 when i ring this one out and find all that needschanging.thanks a gain. jaybuilt
What a fantanstic way to try and tame the “Green meanie” the uk lawwas changed because these beasts were known to be killers. In the70′s they had the power but handled like a trash can. My friend hadone and it would a regular thing to see him wrestle the bike rounda bend. they were evil. A beautiful concept and a fantastic way torecycle some of our older bikes.
Just an FYI…a full article on this motorcycle was printed in thelatest issue of Custom Fighters magazine, available throughcustomfighters.com =)
whats up jay. love that tripple. nice work.
September 11, 2009 at 12:42 pm
Jay, nice work on bringing the traditional cafe racer style to amonoshock streetfighter bike! I would be interested in your 750version and how it turns out…
These old Kaw triples were evil in their day…too bad they were insuch crummy chassis. I wanted one when the 750 came out but collegeand the like got in the way. Eventually settled for a 750 Hondafour, and it was a good choice for my needs. Wasn’t as flimsy asthe Kaw triple, but being an old 2 stroke fancier, it wasn’t asinteresting to me, either.
September 25, 2009 at 12:02 am
Simply stunning. Beautiful custom. I’ll bet it’s a hoot toride.
September 26, 2009 at 11:49 am
Great looking,very cool motor and a bike i would own no problem,but how does it handle at speed around the track or road as thefuel load gets lower? The NS 500 Honda was terrible with theunderbelly tank.
I like it in bits and as a whole
video added to post above – “The Kneeslider”
You absolutely rock. Something like this would sell millions ifcompanies had the balls to build them. Exhaust totally kicksass.
Thanks for reclaiming that song, too. It never belonged withCadillac and the Bonham’s had a good relationship withKawasaki.
thanks all glad you like it .thanks for posting your thought`s onthe bike .the 750 model will be street registered with larger tankand a battery.thanks again .
I’m rather astonished so many people find what they think arefaults with the bike instead of admiring the craftsmanship and allthe things that are right. It’ll get hot for the rider (apparentlynot, its got shields and the rider isn’t complaining), the fueltank is in a bad place for possible contact with road debris (ohyou mean like the car you go to and fro to work with everyday?),the fuel will slosh around and make it unstable (Um, he mentionsfuel cell, as in having foam in the tank which keeps that to aminimum once again the rider seems to have all his hide and thebike is intact, guess its ok). The thing apparently works, itslight and the rider digs it, so whats the problem?
As a long time enthusiast of Kawasaki Triples (I grew up on them) Imust say this is an amazing build.
A major obstacle when modernizing these bikes is dealing with the 3“voluptuous” expansion chambers. There is almost no good way toroute them without ground clearance/cornering issues, or bodilyharm issues from the exposed pipes. The Jaybuilt bike takes aradical approach unlike any I have previously seen and succeedsbeautifully. Unlike some commentors, I completely understand thereasoning behind the belly tank and applaud this builder for hisbrilliant problem solving skills.
Is there any way to get a ride on this beauty? If so, sign meup!
I had a very similar idea to this bike some years ago, after seeingan article on the Bimota Supermono, which also had its gas tankunder the engine for lower CG. I planned to use a Suzuki T500engine and a 1987 CBR600 frame, but same concept. The two chambersof the Suzuki parallel twin would take up a little less space thanthe three of the Kawasaki, and I would just have used the upperskin of the stock tank as a heat shield. Biggest issueI had withold two-stroke was ground clearance in corners. I figured routingthe chambers over the engine would solve that. Glad to see someoneelse was as crazy as me!
I just found this by coincidence,maybe the lights are alreadydone,if not an LED back light between the exhaust and tailpiecewould work and fit I think.Headlights,something small…and forspeedo also a small digital unit,then they don’t take away from thedesign,which is pretty cool!cheers,andy
Hi I’ve just found this & think its a great design. As otherssaid the spannies dont run *that* hot so should be ok under aninsulated cover.
I’d like to see the fuel tank with a curved front end and it doeslook like the centre pipe will get hit by the front wheel on fullbump. That could be solved with a Hossack front end and give evenbetter handling.
On the subject of strokers, the expansion chambers are tuned tosuit the revs where the engine makes max power. Gasses exit theexhaust port with a bang as the port open suddenly (unlike poppetvalves that ramp open). The shockwave expands down the divergingcone creating a suction behind it that pulls mixture into thecylinder and down the pipe. the shockwave bounces back of the farend of the chamber and pushes the mixture back into the cylinderjust before the port shuts. Due to gas inertia the cylinder isfilled from both sides. During the closed period gasses emerge fromthe stinger pipe.
The pipe’s overall length is governed by engine speed. Often thereis not enough length if they are run out the back of the cylinder.High revs allow a shorter pipe but strokers rarely work above10,000 rpm.
All this is about the speed of sound in a hot gas so thetemperature and pressure all affect how it works. Add in theporting etc etc and its complex stuff to get working right. Allthanks to Walter Kaaden, the guy who designed MZ engines in EasternGermany after WW2. He never patented his invention and diedpenniless.
September 10, 2010 at 11:22 am
Could you include the video again? I found it on youtube if youhave lost it
I love the project
Thanks in advance.
I have a video of a test run for ya. thanks jaybuilt
Simply the best looking motorcycle I have ever seen !!! some issuesthough – I believe that Honda tried a similar fuel cell arragementon one of their 2 stroke GP bikes some years ago but foundunslveable centre of gravity issues with the fuel slosshing aboutso low in the set up. Also Hot Balls ????? Dont mean to nit pickthough – I want one !!
obvious issue here is the expansion chamber routing (forcing thefuell tank under the motor). I am trying to think of a differentrouting system (so far unsuccessfully) and still retain theBEAUTIFUL effect – any ideas.
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