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xr80 klx 110 piston

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adikal

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Discussion starter · #1 ·
hey

i have just started doing this conversion as i wanted to now if it will work
i have just bored out my cylinder on my standard xr80 to suit the klx piston
i have dummied it up and it seems to be all good deck height is 2mm below its a bit low on compression
i will mill down the cylinder to get acurate deck height
my concern is the timing chain now it is loose and when i set the timing up "T" on the fly wheel to case and
cam chain dot at 12 o'clock its very hard to start and when running it wont idle runs like absolute shit
has anyone out there done this before help is needed
do i need to dial my cam in ? to allow for the timing chain being looser now ?

any help will be a big help

Thanks
 
#4 ·
the xr 80 has a goofy comp height from factory. in order to run a common comp height piston you have to swap rod to a 94mm rod. if you truely have a +3 mm rod and a piston w/ a comp height of 13mm (from top of wrist pin hole to timing edge of piston) you don't have to deck. with information you have given that it was around 2 mills in the hole i feel pretty confident you do not have a +3mm rod in it, that you actually have a factory rod.

now what do you do that you decked the snot out of everything? theres a few ways you can go about this.

1- assuming you can still get timing chain to tighten up. slot cam sprocket and degree cam back to factory specs or personal spec

2- if you decked 0.110"/2.794mm off cylinder swaping timing chain sprockets both crank and cam from 14/28 to 15/30 and dropping to a 86L chain will restore your chain tensionion. worthy not you CAN NOT use a factory xr 100 crank sprocket on a xr 80 crank. the ID of the xr 100 crank sprocket is larger than the xr 80. now if you can work your magic w/ a kitaco dealer. the kitaco 56.5mm crank the sprocket on that has the proper id as the xr 80 then find yourself a xr 100 cam sprocket and your in business

3- split cases press crank apart put a 94mm rod, make cylinder spacer plate to the same thickness that you removed off the cylinder and give her hell


4- purchase new cylinder rebore, press crank place 94mm rod then no spacer plate needed and run.
 
Discussion starter · #5 ·
Hi storminnorman cheers for the advice I haven't milled.down my cylinder yet and I do.have a +3mm rod the it atm I.purchased the.rod.through firepower minis when you sit the standard klx piston in the motor without the + rod your deckheight is -5 mm I have now placed in the +3 mm rod to get the deck height of -2mm so I will now mil the head down 1mm to get half reason able comp out.of this I will.try and alter my can gear so I can dial my can in after the machine work I'm just hoping I.can get good tension out of my chain
 
#6 ·
-5mm deck without long rod. May be a dumb question but are you 100% you have a xr 80 cylinder and not a xr 100 cylinder? There os a difference between the 2. The xr 100 cylinder is taller than the the xr 80 which if 100 cylinder was used with 80 crank you would have about a -5mm deck.
 
Discussion starter · #7 ·
im positve the bike has had one previous owner and they had it since new its a 2000 model xr80
i have 2 cylinders i will check them both the second one i brought because i couldnt get this big bore kit to work
i am really appriciating your ffedback your the only person who actually seems to care hahaha
i will keep you posted on this build i will measure the 2 cylinders today and let you know the outcome :)
other with i will just get the 120cc kit from firepower and be done with this once and for all
do you have to machine the case with there 120cc big bore kit ????
 
#8 ·
Lol not many guys are into the upright citizens on here. Me on the other hand the ole xr 75 is what got me into pitbikes. I tried the 50/70/110 thing not for me ha ha went back to the 75/80/100.

If you have xr 80 cases you will have to case bore for the fpm 120 kit. Be careful case boring the oil passage is set closer to case bore than xr 100 cases. If I remember correctly Terry uses a 62mm od sleeve which you get mighty close to the oil hole.

When mic-in cylinders a xr
 
Discussion starter · #10 ·
well i think i found the no comp issue when i had the head poslished and small port job the dunder klunder didnt lap my valves
when i did a valave leak test they were pissing out !!!!!
i have now lapped them in and ready to put this weapon back together !!!!
will keep you posted on the end result and give a full run down on the build
 
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