CR 125 1983 cylinder

billyslad
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billyslad
Edited Date/Time 1/11/2015 11:52pm
I am rebuilding a 1983 CR 125 and the barrell is shot , I have a 1986 barrell and wonder if anyone has ever fitted this on as a mod or hop up The bore and stroke for an 83 is 55.5 x50 and the conrod is 100mm the 1986 is 54 x 54 and the rod length is 104mm

My thoughts were to put the 86 standard cylinder on to the 83 engine using the longer rod from the 86 as well

Any help would be much appreciated
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berniepiet
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berniepiet 1/1/2015 8:28am
1/1/2015 8:28am
Let us know how it works. I am looking for more power out of my 83
billyslad
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billyslad 1/1/2015 2:29pm
1/1/2015 2:29pm
What have you tried so far , I was hoping the 86 cylinder and rod would go on and work well I would like to combine with a 36mm Airstriker Carb as I have modified a 86 airbox and subframe to suit so that should give more air

A few more mods to the subframe and the 83 seat and side panels should work

The exhaust will have to be an extended 86 somehow as I cannot use the ATAC system

I am just trying to formulate a plan atm so any ideas are welcome

I intend to race in the uk at some pre 83 events
kelroy_leon
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kelroy_leon 1/2/2015 5:13pm
1/2/2015 5:13pm
The base gasket has a different # from Honda, that could be a simple issue or possibly the stud spacing. The studs are also a different listing. Are the diameters the same? The base diameter of the cyl may come in to play. Simple turning it down or machining the case would solve that. Giving Eric Gorr a call might shed some light on the for you. You could still run the ATAC manifold, just block off the opening for the canister.
Dick Trickle 1/2/2015 9:14pm
1/2/2015 9:14pm
You didnt say what was wrong with your cylinder. If it is the bore worn out, consider a resleeve. I have just sent a 83 YZ125 cylinder, head and powervalve to Eric Gorr at Forward Motion. He is going to resleeve it back to standard size, port it, match powervalve, machine head, bead blast the lot.. Will be like new and go like a rocket. He is also going to match up a Wossner piston and send the whole lot back to me in Oz.

The Shop

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billyslad
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billyslad 1/4/2015 6:13am
1/4/2015 6:13am
there is nothing wrong with the cylinder howver the 86 made more power so I thought an 86 cylinder if it would fit and then tuned and ported would be better place to start than an 83

billyslad
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billyslad 1/11/2015 4:37am
1/11/2015 4:37am
Started work on the bike today and with the barrel off it is at the end of its life, can't quite work out what has gone on but sure the marks at the base of the cylinder are not supposed to be there

tns
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tns 1/11/2015 10:46am
1/11/2015 10:46am Edited Date/Time 1/11/2015 10:48am
with all those changes you won,t be able to use it at the pre 83 championship only allowed to use stuff from that period when i bought my 83 cr125 it had an 84 barrel and i had to change it send barrel to pj engineering cost you £140 to have a new sleve put in
tns
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tns 1/11/2015 10:55am
1/11/2015 10:55am




This is mine from when i got it to now,i have just added a new dg exhaust to give it some more power
billyslad
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billyslad 1/11/2015 11:10am
1/11/2015 11:10am
very smart resto tns , thanks for the advice how did you et on with the clutch/ waterpump issue ?
StevieD113 1/11/2015 11:29am
1/11/2015 11:29am
billyslad wrote:
Started work on the bike today and with the barrel off it is at the end of its life, can't quite work out what has gone...
Started work on the bike today and with the barrel off it is at the end of its life, can't quite work out what has gone on but sure the marks at the base of the cylinder are not supposed to be there

That barrel isn't scrap at all! It just need re-lining. It costs about the same as having a barrel re-plated.

Stevie
billyslad
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billyslad 1/11/2015 11:47am
1/11/2015 11:47am
I will bring it up next week with the 99 Steve and you can see what you think
A resleeve should sort it
tns
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tns 1/11/2015 11:52pm
1/11/2015 11:52pm Edited Date/Time 1/11/2015 11:53pm
my waterpump area was pitted and leaked so i sent it to stevie denton at Denton Engineering and he did a fantastic epoxy repair on it for £120 and it has been fine since and that was in 2013,so it has held for 2 seasons so far.You could bite the big one thou and pay £420 for a new alli one from evo's are us.My spare bike had a totally shot casing but i was really lucky and my mate sold me a really good one.I have 2 complete bikes and at the moment i am building a spare engine which is nos from the cases up i do need a waterpump case for it thou so might need to get the alli one but that would mean the engine owes me about £1000

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