Big bore xbr

[JOOLZ]

Hi I have just been offered a new and unused xl600 barrel and high compression wiseco piston, can anyone tell me if its a straight replacement to fit this barrel and piston (100mm) or do i need the crankcase bored to accept the larger size

[SteveC#222]

I'm not 100% certain but I think if you use the XL600 barrel you have to ease out the crankcase mouth a bit. Usually they use an XBR barrel, press out the liner then rebore to accept the XL600 liner. ( I understand you can bore out the xbr liner but it leaves it mighty thin)

*** Important Bit!!.... You need to make sure it's an XL600R barrel as they were the same stroke as the XBR -XBR 92x75 XL600R 100 x 75. Apparently the later XL600 RM/LM had a smaller bore and longer stroke - 97 x 80.

I don't know if you've seen this before

http://www.champsclock.com/gb500hu.htm

Maybe someone with a spare XBR barrel can measure it for you?

[SteveC#222]

a further thought, I seem to remember that you need to get shim made to bring the little end down to 22mm (XL600) from the standard XBR size of 24mm so the gudgeon pin will fit, I assume this would be the same for a Wiseco.

[JOOLZ]

Hi thanks, its an xl600r, the the small end pin looks the right size but i would have to measure it up against the standard xbr pin

[blew]

I have fitted an XL600 barrel and piston to my XBR.They were a straight swap.I used two base gaskets to keep the compression to a reasonable level.There was no need to open the crankcase mouth or anything else.A simple swap.I obviously used an XL head gasket.It pulls well now.

[guest564]

I've done several of these and did have to open up the crankcase mouths a couple of mm, this was on early XBR engines. The XL600LM also has the longer stroke engine so avoid that one too. You only need to bush the piston when you use the 92mm XR500 piston on the XBR.

[blew]

My XBR was registered in 88.I wouldn't know about earlier models.

[JOOLZ]

Thanks for everyones help, I think I will get the kit and fit it over winter after my tax runs out, (and no im not a fair weather biker, its the first winter its been off the road lol) I think I have an early model 1984 so it looks like i will have to get the case bored out a little

[JOOLZ]

Oh dear major problems, the guy couldnt find the piston but I decided to buy the barrel as its new, and thought I could get a piston for it else where, well I have spent the last couple of weeks trying to track down a wiseco piston to fit the standard bore and found out they dont make them any more. Several companys have them listed for sale on ebay, but on inquiry I find there are none in stock. So Im a bit stuck, Does the xr piston have its pin set at the same height as the xl, if so I could use an xr600 with a 3mm oversize. Are there other companys that do a standard 100mm size performance piston for the xl600. Any help would be appreciated

[themoudie]

Aye Joolz,

I sourced SRX/XT Wiseco parts from Eastwood Racing, Swanley, Kent : Eastwood_Racing

Have you given them a try?

My regards, Bill.

[guest564]

I used to get my stuff from White Bros in the US, I think they're gone now but you could try Wiseco themselves. Otherwise JE used to make some pistons for them as well.  I think the longer stroke piston has the correct height but the gudgeon pin is the wrong size. All my stuff is in storage so I'm afraid I can't check, again Wiseco should be able to advise.

[JOOLZ]

Hi thanks. I have tried Wiseco with no luck, so I will give JE a call. If the worst comes to the worst I will have to fit the standard piston, I will still have more compression as its about 90cc more capacity being squashed into the 500 head

[blew]

My 600 is on the standard XL piston,with two base gaskets.I'm no lightweight,but the kickstart won't move the piston over TDC without the decompressor.Tremendous compression.

[guest564]

I can just about kick over my XBR with 600cc 11.6:1 Wiseco but I do have to put it on axle stands and then kind of bounce on the kick start to get it over TDC. If it kicks back it really hurts!
I'm not sure that you will get a lot more compression with the XL piston on its own, as I recall there isn't a lot of difference in the size of the combustion chamber, the XL has a more heavily dished piston.

[blew]

With the amount the kickstart swings out from the bike,when I really give it my full weight,the bike tilts sideways.