Tuning your Zxr 400......

[tng21]

Well when i get my Zxr on tuesday, i wana start looking at a few mods to suit me, new rear end , small indicators etc.

Just a question about what i can do to spruse the engine up a little. Its got a Art racing can so just thought what else could be done. Nothing major, just things to compliment having a race can.

Filters?, dyno jet? blah blah. y know, just small tweaks that will help.

[gubbs]

Most people start with an exhaust & jet kit ,buy the best if it's available Acropovich exhausts as seen on nearly all world superbikes are well made & light ,beware makers who claim large hp increases as these will have bigbore downpipes & reduce mid range.The ZXR is one of those bikes you can't get an acropo for so I used an italian titanium road system with a race can.The micron race system works well on the ZXR .Race cans have little effect on performance as long as they are well made & light ,it's the downpipes that control engine performance.

Choice of jetting can be difficult ,different manufacturers kits work better in different situations .It's mainly the needle that's the problem they're never perfect ,usualy slightly to rich or to lean in the mid range once you've adjusted the top end.On the ZXR with no air box or with lid removed ,I found the dynojet needles were reasonable ,if you drop them to the lowest setting .I use 108/110 dynojet mains withh the aircorrector hole blanked.Idle 2.5 turns from fully in.The can ,airbox & exhaust should see you upto 63hp.Make sure you have the 32mm carbs ,also check bellmouth rubbers for shrinkage as they can get down to 26mm ,not much use to a 32mm carb .I make my own bellmouths .

Next it get's expensive with cam ,compression work & head flow.There is only one possible cam choice for the ZXR as nobody else does one ,that is Kent cams regrind of the originals (it can only be done to euro bikes cams as there's not enough metal in the jap one's).You will also need adjustable cam sprockets ,which we make, so you can set the cam timing .You will also need shims a lot thicker than standard ,which again I have to make.

The porting is quite simple but time consuming ,it involves cleaning the steps away from the back of the valve seats ,knife edging the intake dividers & matching the intake rubbers to the ports.Japanes cylinder heads a very good already so you're just tidying up the casting.

Compression & squish ,you need to bolt the whole thing together so you can measure vavle to piston & head to piston clearances .On the ZXR you can remove the base gasket & skim 0.5 mm off the head .Now you're upto 66/68hp.

As you can see it's a longwinded process for quite small gains & the cost is mainly in the man hours ,though from what I've told you here you can have a go yourself if you like .I have seen some ZXR engines with lightened cranks ,I was unable to measure any difference this might have made on the dyno .It is supposed to help the engine spin up quickly ,but it can also cause the engine to loose inertia making starts harder.

There were quite a few more tricks involving race airbox mods ,ignition and more severe engine work ,but they are alot of work for the last few hp's .

http://www.versatilemarine.co.uk/spike/tuning.htm

[tng21]

hmm lol i dont think ill bother then. Its going to have a art race can but thats about it i think. Have seen new downpipes on ebay for about 200 so had thought of those just coz they're new and not the old crappy rusty looking ones that are on my friends but we'll see.

cheers