BIG BORE KITS and alternatives

[tk400]

How are you all going, As far As I understand there are a few expensive options here
TTS
BEET
some american company that also makes the pistons for TTS?
and another company that boasts a 460cc kit?

anyway at this point I can only remember the name of the first two.

Started this thread to discuss options, I am thinking that there may be other pistons in the kawasaki range worth looking at. I was thinking the zzr250 61.00mm bore. The question is what are the valve reliefs like on these pistons and the pin to deck height. Also need to know pin bore etc.

just curious about the zzr option, but mostly want to discuss benefits of big bore kits and disadvantages. here are the pro's as I see it :

1. obviously larger CC
2. higher compression ratio possible due to smaller combustion chamber to cylinder ratio
3. Better squish band
4. improved midrange due to effectively smaller valves and porting carbs etc
5. better piston strength from the forged bore kits?

disadvantages

1. probable heavier piston mass
2. due to above ( if true) lower max piston velocity
3. possibly extensive modification including porting , larger valves etc. in order to acheive the same rpm range with larger CC
5. COST !!!!!!!!!!!
6. legality for racing....although one could destroke and acheive a higher reving 400cc engine
7. piston quality debatable

anyway I will wait for further comment...

cheers

regards TK400

[will#224]

I raced supermoto for a few seasons and big bore kits were popular for easy big power. The main problems encountered were crank bearings breaking up, con rods snapping at the small end and trying to manage the extra heat that comes with more power and sometimes smaller barrel to water jacket sizes. Things wouldn't last long if you tried to make them rev as before. The best kits included new cranks, bearings, rods, pistons and a bigger valve head to make use of the more fuel air that could be used.

It does work though, there were a few 700cc husabergs, 612cc ktms and the 525cc honda crf but there were too much of a handfull on smaller tracks and sometimes the 250cc bikes would put in more consistant times with the 450 being the best alrounder.

[zimm]

there's a 45X kit available from germany i think ..

main issue's as you guessed are lower rev limits due to the greater weight of the pistons putting bigger loads on the conrods and crank (L9 would be best base for a big bore).. and even then, its hard to guess at engine life as every one is a one off ..

there are some +1mm pistons available, but i dont know the specs.

from what i can gather most of the "kits" are JE piston kits being re-sold by various people.. its certainly the case with the TTS kit, although i believe Beet probably make their own pistons.

[tk400]

Thanks for the input so far, one of the main things i am interested in is aftermarket pistons. And while on that track got to wondering about the viability of capacity increase. I want to get some more compression, Im at 13:1 at the moment but want to push it to like 14.5:1 if possible and run on alky.......At the moment I have .6 piston to head , standard bore and milled the head to the seat insert just begins to be cut into. I am hoping that r0045j-10 race plugs will increase comp a little due to the design of them. also looking at flat faced valves. But thaey are as expensive as a big bore kit..LOL. short of all that im running out of methods other than the big bore option that straight aaway increases comp dues to the cylc vol to chamber vol ratio increase. I wonder what the F3 kit pistons are like and if they still exist. I think they had like an extension of the pent roof part of the piston.....???....anyway just rambling out loud... cheers,


regards TK400

[zimm]

cr9-eks will give a higher CR than the R0045's mate .. just cos there's more of them in the combustion chamber.. but the cr9's wont play nicely with pent roof high comp pistons .. least they didnt in my zx6r .. little dings in the piston crowns from saying hello at high revs

thought about skimming the barrels and then the piston crowns to bring the squish back ?

you can also (so i've heard) skim the head on a slight angle to both raise CR and improve flow without running into clearance issues due to the diff in in/ex piston/valve clearances .. although .. ive not looked into it or given it much thought ..

i've heard of 15:1 CR's on zxr's .. but how .. im unsure.

[tk400]

Hey zimm, yeah i wasnt thinkin about the electrode on the CR9's ( doh ) but was just thinkin that because the roo45's have no quench valley, that they may displace more of the chamber. but yeah I reckon your right. But as you say at least it allows the pent roof to get closer. As for the barrels I allready skimmed em to bring the squish to .6 so kinda cant go much further there. Im glad to hear that it s possible , 15:1 would be sweet....dont know how the hell the starter motor will handle it...LOL.....

sounds to me like its gunna be all in the pistons and flat valves.

although increasing the valve mass is not my idea of safe in these engines, So I will stiff with pistons first. cheers for the replies.

By the way does anyone have a pair of adj cam sprockets they wana sell...cheers

regards Troy

[zimm]

what i mean is, skim the barrel so the pistons are relativeley higher at tdc, then machine the squish band and valve pockets to give the required clearances, puts more metal in the CC and would raise CR a fair bit, also reduces piston mass, but the machining on the piston crowns would be extensive.

adjustable sprockets are essential really, timing can go quite a bit off once things get skimmed.

and sorry, no, havent got any spare.. only got mine this morning

you can adjust the stock sprockets though .. they'll come off/move with the correct application of heat.

starter motor ? pah ! proper bikes are bump started !

[tk400]

yeah I get what your sayin now zimm, sounds like a good option. will take out the base gasket and head gasket, then use bearing blue to get a good fit with the combustion chamber and squish area then when I put my gaskets back in I will have my clearance back...sounds like a plan...LOL. I know cosworth does this extensively so with time and effort and hours on the dremel....should be good...lol.

Id like to bump it.....but its my sunday mountain/coast road weapon. need to be able to stop for pies and coffee......read as : i am a fat lazy giraffe.......lol

cheers

regards TK400

[AFM327]

The JE pistons are heavy, the beets are cast and almost as light as the stock pistons, Very nice pistons. My motor builder built a 440 using the beets a couple years ago. It had good power but they initially had difficulty getting it to seal well as the 3mm over doesn't leave a lot of material between the cylinders. Once they got it sorted it was real fast, fast enough to beat the fastest SV's. I've looked at getting some 2mm over pistons from CP made, as my racing org (AFM) actually allows 450cc. It's a throwback from the old 450's, There's also WERA which I haven't raced with yet and they allow 490 in their D superbike class which is where the ZXR would be the most competitive. Don't think it would be worth the time and money to try and build one to that spec as it would have to be stroked too.

[tk400]

How are you goin, I have just been reading in "moto tech" about the small bore superbike class in america. they were building an rvf400 of 450cc with carrillo rods and all. Are there any people over there doing similar to ZXR's
what pistons do they use. what about machining some from another new model zx6 maybe. are they of an appropriate wrist pin dia and cent to deck height?.....cheeers

regards TK400

[AFM327]

Got a link for the moto tech site? I'm pretty sure it's the guys I've been racing against. Here's a link to what they have been doing, lots of dollars invested and their goal seems to be what Roger Middleton has achieved. . http://mngforce.typepad.com/ They guy building the motors is Mike Norman, he's a honda guy, imported some VFR's several years ago. The 400's, with the exception of the FZR in 1988-90 were not imported to the states, so there aren't very many. Another shop in Sacramento GPCmoto, which I think is closed now as I haven't been able to reach them imported some race bikes too, honda, and kawi. That's where I got mine from a few years ago. Tim the owner from GPC built a 440 using the beet kit. Actually my motor builder built it, so I know what it took to get it to work. They had problems getting it to seal well. Once they got that sorted it made about 10% more Hp than my bike. There's dyno sheets on my builders site. http://www.perf-concepts.com/index.htm

Tim stopped racing, had his bike for sale, don't know if it ever sold. I have two ZXR 400's one with the motor under construction right now. I know of three other ZXR's, one guy has two, and H and an L, he's disappeared from the bike scene after crashing and breaking a hip a few years ago. I'd love to buy his L model if I could find him again. He had a set of PVM's made for it which I'd love to get. Another races his once in awhile, it's pretty much stock. My bike is an SP model, has 0.5 oem pistons and head work, kawi kit airbox, and flatslides, 636 forks which are more for the brakes than the forks themselves. So no real superbike in the mix. I'm going to build one at some point. Small tank like the RMKD bike, probably carbon, mag or carbon wheels, 2mm over custom pistons, I'm looking into some of the aftermarket CDI's now. I've taken some time off from racing to work on the house but I'll be back part-time this year and try for another championship in 2010 when I turn 50.

[zimm]

I'm looking into some of the aftermarket CDI's now.

i can wholeheartedly recommend the ignitech ignition units made in the Czeck republic

programmable curve, 2 or 4 channel (for running stick coils properly) shift light, variable rev limit .. and very cheap @ about 130 euro's.

I imported a bunch of them a while back, run one on mine and the rest are getting rave reviews with the vfr/rvf crowd.

[neil_cb125t]

the TTS kit is pretty solid - over here the rules allow up to 450. as we compete against Svs. we have no rules on anything really. they have just started taking 600 proddy bikes loppin of a cylinder making it a 450cc triple.......

My bike has tts 444cc kit - ive balanced the crank and lightened and shot penned the original rodes. i have standard h cams - porting with flat slides No air box - and still running A FLYWHEEL with the small H radiator. i have went from 66 to 80 RWHP after doing the above. she is reliable as. still on its orginial valves... but im replacing those this week.

the bikes can handle as much compression as you can give them as long as clearances are good. We have a "local legeand" over here who is the Z man. his record is 92 RWHP.

Just measure everything - and dont rev it past 14k but its the best thing you can do!!

[tk400]

so the TTS kit is only good for 14,000 rpm you reckon....I would prefer to not drop my max RPM I have quite large cams and need to at least see 15 000 to 15 500 or so or will be throwing away alot of volumetric efficiency potential. maybe the beets are better ? ...anyways what about other standard pistons from other models of bike has anyone played with that. cheers


PS would love to hear more about what you guys do to your 95 HP beasts....is that alky or petrol.....

[dynopro]

i have done many motors using the 444 kit it is a good option. The power these bikes can make is amazing compared to any other 400 on a dynapro dyno i have seen over 86rw bhp (easily over 90bhp on a dynojet dyno) and motors still going strong running a taller rpm limit than stock. A lot of time has to be spent getting the deck height right and piston to valve clearence correct using sp or kent cams. The pistons are very heavy stock and require a lot of time consuming machining to get the weights bac k to a tolerable level. The big problem when doing these is that the over hang area of the bores in the barrels becomes very thin when they have been taken out 3mm this is a problem and with the thrust faces of the piston hitting hard the barrels will become oval very qiuickly, i have seen these chip and break away at the bottom the only way to prevent this is to replace this at regular intervals ( end of season for most).


I cant see without stroking the crank how it would be posible to go extra on the bore size a linner option i dont think would be available here without some serious modification.