Engine mod
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- Posts: 32
- Joined: Mon Dec 10, 2007 8:05 pm
- My Bike: ZXR400 Race bike
Engine mod
Hi, ive been told when you have removed the chargeing system from a ZXR400L1, you can remove or grind away the fly wheel so you can replace the bulky casing with a flat plate...now is this true or does it affect the engine balance, can you just grind the fly wheel down a little so it saves weight....any info on this would be great as im building a race bike for next season.
- stu71
- zxr400 oc member
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- Location: S.Yorks
Re: Engine mod
Have a look on ebay (zxr400 race flywheel) there is a modified one there, easy to turn yours into that, hope this help Stu
- Ballsout Racing
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Re: Engine mod
Could be true(about fitting flat plate), but you'd also lose the starting system.Jerry wrote:Hi, ive been told when you have removed the chargeing system from a ZXR400L1, you can remove or grind away the fly wheel so you can replace the bulky casing with a flat plate...now is this true or does it affect the engine balance, can you just grind the fly wheel down a little so it saves weight....any info on this would be great as im building a race bike for next season.
IIRC the flywheel is rivetted onto the crank, just completely remove it, don't understand why you would want to fit the smaller one that's on ebay


- stu71
- zxr400 oc member
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Re: Engine mod
Rivetted onto the crank ?
not stripped mine down for a bit but isn't the starter motor gear mounted onto the small part of the flywheel, thats why you have to use it ? thats if you use a starter
Stu

Stu
- Ballsout Racing
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Re: Engine mod
Yeah, you could be right, after writing that I had second thoughts. I just can't remember and it's frustrating me. I just seem to recall the complete flywheel coming off, but, I do have the starter working, maybe old age is getting too mestu71 wrote:Rivetted onto the crank ?not stripped mine down for a bit but isn't the starter motor gear mounted onto the small part of the flywheel, thats why you have to use it ? thats if you use a starter
Stu

- stu71
- zxr400 oc member
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Re: Engine mod
I'm sure you will have it on because if my old brain works the starter flywheel goes into the spring loaded bollies on the back
- noelb
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Re: Engine mod
The starter hub runs on one-way bearings on the hub of the Alternator flywheel. The bulk of the flywheel, i.e. the magnets and the rest of the high inertia stuff, is rivetted to this hub. these can be drilled easily. The hub is held onto a taper on the crank with a bolt. It is important to either leave this hub in place or block the oilways to the starter assembly or you'll have no oil pressure adn bloy all kinds of hell outta yer engine.
Hope this helps!
Cheers
Noel B.
Hope this helps!
Cheers
Noel B.
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Re: Engine mod
I Haven't got a starter or generator on mine but i'm fairly sure the end of the crank sticks out further than the engine casing. It would be interesting to know if anyone had gone down the flat plate route because generator covers are getting expensive to source.
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Re: Engine mod
Hey,
the bike i have started racing has had this mod done to it, my workmate who raced it before me did it, you have to machine ( not grind ) the end off the crank and drill and tap it ( i think we used a 10mm grub screw and lots of LOCtite hyraulic sealent, we replaced the side cover witha piece of ally plate and a 10 mm piece of teflon lust incase some thing tries to hit it in a bad crash.

PS make sure you have a realy realy good seal on the crank oil gallery, or you will spit No.1 bearing
the bike i have started racing has had this mod done to it, my workmate who raced it before me did it, you have to machine ( not grind ) the end off the crank and drill and tap it ( i think we used a 10mm grub screw and lots of LOCtite hyraulic sealent, we replaced the side cover witha piece of ally plate and a 10 mm piece of teflon lust incase some thing tries to hit it in a bad crash.

PS make sure you have a realy realy good seal on the crank oil gallery, or you will spit No.1 bearing
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Re: Engine mod
does this mean the battery wont charge,?
- jake
- zxr400 oc member
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Re: Engine mod
yes, no battery charging and only bump starting mate
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Re: Engine mod
bang on, we have fitted a small conector under the tail piece that after a race we wack the warmers on and a charger into the plug, the bike only ran a tiny wee batery from a scooter. this would run for a good 4 hours riding on a test day too with no charge.
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Re: Engine mod
does anyone have any idea of minimum weight on a zxr 400,when ya goe this extreme with the choppin!
- jake
- zxr400 oc member
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Re: Engine mod
140kg odd rmkd had his down to i think, might of been less. light tho 

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Re: Engine mod
I'd imagine there would be a power increase gained from removing the rotor.....................less drag on the crank