How much is involved with the 444cc Big Bore

[spaz]

I can't seem to find anything on this forum regarding the big bore, but I know at least one of you has done it.

From what I can see, unless my engine needs a total rebuild, I think it would be cheaper for me to onsell the 400 and buy a 600. Especially when the TTS kit costs 400 pounds + labour + extra crap, and to top it off I live on the other side of the world, i.e. $$$ shipping! Still, out of curiosity, What's involved with it?

do you need to play around with the top end (cams, valve timing and valves)

does the standard 400 head gasket still fit or do you have to get a specially designed one?

Has anyone had clutch problems that have arisen from the power gains?

How much work has to be done to the carbs, air box and exhaust, if any at all?

What exactly comes with the kit that is custom designed for the job/can't be replaced with oem parts?

Are custom JE pistons a competitive option or is it more hassle than it's worth?

Other than the bore, hone and dyno work that is required? I reckon even I could fit some pistons. Is playing the backyard mechanic in this case a good Idea?

Cheers all. If there's anything that you can think of that I might need to know about, throw it in as well.

[masterofinsanity]

as far as i'm aware only Jamz has had this done by TTS and i don't think he was that impressed with their service.

[gubbs]

I honestly wouldn't bother tbh.

The expense, the hassle and the inevitable endless tuning and fuelling adjustments coupled with the almost assured explosion at the end of it would be best avoided; spend the cash on a 600.

In the states they're still making ZX6r's and badging them up as ZZR's.



Great bike, great price!

[RedexRobB]

fugly tho.

[rene]

personaly quite like the, good bikes to ride as well take a thrashing well! and keep up on fast rides as well

All round good bike imo, even more so for the money that they go for now!

[Jamz]

I can't seem to find anything on this forum regarding the big bore, but I know at least one of you has done it.

From what I can see, unless my engine needs a total rebuild, I think it would be cheaper for me to onsell the 400 and buy a 600. Especially when the TTS kit costs 400 pounds + labour + extra crap, and to top it off I live on the other side of the world, i.e. $$$ shipping! Still, out of curiosity, What's involved with it?

do you need to play around with the top end (cams, valve timing and valves)

does the standard 400 head gasket still fit or do you have to get a specially designed one?

Has anyone had clutch problems that have arisen from the power gains?

How much work has to be done to the carbs, air box and exhaust, if any at all?

What exactly comes with the kit that is custom designed for the job/can't be replaced with oem parts?

Are custom JE pistons a competitive option or is it more hassle than it's worth?

Other than the bore, hone and dyno work that is required? I reckon even I could fit some pistons. Is playing the backyard mechanic in this case a good Idea?

Cheers all. If there's anything that you can think of that I might need to know about, throw it in as well.

Whew, where to start?

First off, I wouldn't trust TTS to make me a bacon butty, after the ammount they fecked my bike up.

Other than that, it is the best mod you'll ever make to your bike! It was like getting a brand new bike, and had the same engine charecteristics of the ZXR750 - i.e. it pulls like a truck from anywhere, and was as fast at 6,000rpm as it was at 14,000rpm before the rebore!

I had mine done because the head gasket had blown, so I figured for another few hundred squid I may as well get it done. They quoted £1000 for the ride-in service, and then charged me £1500!

I believe the head gasket used is upgraded, and if I remember correctly, the TTS kit uses JE pistons. I'm sure if you email TTS they'll confirm the exact mods and head gasket etc.

Other than that the rest of the bike was standard, and just needed a few dyno runs to sort out.

If you have the money - do it. You won't be disappointed. I can't see any reason why you couldn't do it yourself - just be aware that if you're doing it while replacing a blown gasket, the head might need skimming as well, so get that checked.

Ooh, the clutch! An OE clutch seemed to handle it ok, but it obviously shortened the life, but there are heavier duty clutchplates on the market.

Before I sold my bike it was jumping out of second gear above 9,000rpm. This COULD have been something to do with the rebore, but to be honest I think it was just the fact that the bike had done 50,000 miles by then.

Do it, do it, do it, do it!!!

[Jamz]

One more important thing, actually!!!

I found that disturbing the loom on a '93 bike cause no end of troubles!

If I did it again, I would fit a new loom at the same time.

[rene]

weird that i had the same problem when rebuilding my 400 soon as i removed some conectors and broke 15 odd years of rust and corosion on the conectors it never worked properly again!

ended up putting in a loom off a L9 in with a meta alarm on it i brought off ebay for £5 (alarm was £280 at the time!) sorted all my problems!

[Jamz]

Yes, it was a very valuable lesson learned the hard way!

I spent many, many hours trying to trace electrical woes afterwards - not blaming TTS for this part, because I think disturbing ANY old loom would have done the same.

(although TTS didn't wire my fucking indicators back in, either! :smt013 )

[SplaTZXR400]

ye i have the bore kit, but i bought it already fitted so never hav known wot a zxr400 is like. but iv bin told that it adds more torque which i must say it does pull well from the very low rev range, iv gone from 30 to 110 in 6th gear with a fat friend on the back, so pull power is good, obviously once it hits the powerband it flies. i hav standard plugs and mixture screw at 2 turns, stock air filter and exhaust, cv carbs with 95 main jets. and my bike runs like a dream. always starts, dont stall, and good power. so as far as i am aware theres not alot else that needs to be done with the bore kit except fit it. my clutch is fine, but wont be surprised if its nearly nackerd the plates, i slip the clutch alot. erm cams valves timing standard. but ye headgasket is bout £65 i was told as its a special 1, but iv had no problems since iv had the peoper gasket. happy borein

[sheehan]

Thought i would bump this instead of making a new topic...

There seems to be mixed views about this bore kit, i was looking on http://www.zxrworld.co.uk/ earlier, and saw this bore kit and was interested by it. For £400 if i fit it myself and got a local company to do the honing on the cylinders, would it be worthwile? And someone mentioned dyno'ing their bike to get it running sweet - what were the power and torque gains?

[SplaTZXR400]

hello mate, ye would recomend dynoin if its a fair price, tho not essential,i have a OffTR bike at the moment with a 444 bore. i dunno bout power gains but i was told it increases torque, iv not ridden another bike with as much power or more than mine so i cannot compare, but it defintaely pulled well. i did balance the carbs myself n have the fuel screws set at 1 3/4 turns out and #95 jets i believe, not sure, bin nearly a year since iv worked on them. but wen it was runnning it was nice. i do have a dyno chart if u wan2 c it, only problem is it was the dyno print of for a restricted 444 obviously 33bhp. if u need more details il look at mine more closely for u if u like.

[masterofinsanity]

is that offtr as in no mot or offtr as in scrambler with a zxr444 engine?

[sheehan]

Sounds good mate, im yet to get a zxr400 but when i do i will pull you up about it again, reading about it has got me tempted lol

[SplaTZXR400]

erm :s offtr as in in pieces, since the accident iv not had the time money or patience to fix it, i mean it runs ok, iv had it up down my road but, ye no mot or tax or insurance anymore. its jus a bike minus front fairing clocks n lil odds n sods. im kinda stuck wot to do wit it, im temptd to sell it cheap for spares or repair, as mechanically n structurally theres nothing wrong wit it. but even if i fixed it up i cant affors to run 2 vehicles i miss my ZXR!!