90s 125 reeds... Rad valve, V Force or stock??

nkoebes826
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10/23/2019 7:41am Edited Date/Time 10/27/2019 6:46am
I just picked up a decently clean 91 kx125 for a bike build and wanted to get thoughts on reeds. As with most older kawasakis ive found the rubber air boot coming off the reed cage has some gnarly dry rotting going on and it will defiantly need replaced. An OEM rubber air boot for the carburetor isn't available but I have found one guy on ebay selling a reproduction (part number 16065-1206 from hotfootmoto-online). If any one has experience with these feel free to share. Then there is the rad valve or v force route. Ive been told good and bad about both but most are peoples opinions on newer 125s. Some people say they are great, others say they are a pain to get your bike to run half way decent with them at all. What are your opinions and experiences on these after market reed cages for these early 90s 125s. Thanks
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SLOWTIME
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10/24/2019 4:53pm Edited Date/Time 10/24/2019 4:54pm
I ordered Jude a chain slider for the kx60 from hotfoot. No problems dealing with them. The slider seems of good quality and it fit nicely. I did put a rad valve on my 94.. But not 100% sure that’s my jetting problem. I’ve had v force on both my 02 rm125 and my 05rm250.. worked very well.
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sandman768
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10/24/2019 5:20pm
Nice find....Usually when a I need the intake boot and reeds for an older bike I get the Boyesen rad valve, as it solves all your problems and replacement parts readily available from Boyesen.
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nkoebes826
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10/25/2019 10:48am
sandman768 wrote:
Nice find....Usually when a I need the intake boot and reeds for an older bike I get the Boyesen rad valve, as it solves all your...
Nice find....Usually when a I need the intake boot and reeds for an older bike I get the Boyesen rad valve, as it solves all your problems and replacement parts readily available from Boyesen.
Thanks sandman. The rad valve is what ive been leaning towards but still not totally sure yet. Do you see a power gain at all with the rad valve or does it still seem relativity the same as stock? Also on some other fourms people were saying they had to lean out the pilot jet to get their bikes to run right with a rad valve. Have you had that experience or does it seem to run fine right after you install it?

The Shop

450exc115
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Hebron, CT US
10/25/2019 12:02pm
There is a good chance your going to have to lean it out if you do either VForce or Rad Valve. The Vforce I put in a 90 RM125 required 2 steps leaner on the pilot and one on the main.

I've run both, Vforce was more low/bottom response with stock top end pull and the rad was more everywhere but not as good as the Vforce on the bottom/mid.
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sandman768
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10/25/2019 1:40pm
nkoebes826 wrote:
Thanks sandman. The rad valve is what ive been leaning towards but still not totally sure yet. Do you see a power gain at all with...
Thanks sandman. The rad valve is what ive been leaning towards but still not totally sure yet. Do you see a power gain at all with the rad valve or does it still seem relativity the same as stock? Also on some other fourms people were saying they had to lean out the pilot jet to get their bikes to run right with a rad valve. Have you had that experience or does it seem to run fine right after you install it?
I have used both vforce and rad valves on different bikes, they are both quality products and good replacement choices. I feel the power characteristics vary from model to model. Hard to say how each one would work on your particular bike. Do not expect massive power gains from either, but proper functioning reeds are essential to your bike running properly. I would start with standard jetting and do some plug chop runs...Pro Circuit and FMF have jetting specs for a lot of the older models, that is also a good starting point. As with all jetting, so many variables it is impossible to just say what will be needed. On my older bikes, where parts are scarce & pricey, Error on the rich side then work my way leaner as needed. Verify what jets are currently in the carb, compare with factory settings, brings some spare pilots & mains in both directions, and go out for a test session, it does not take very long to swap jets on a 2t. Of course this is all assuming the engine is in good operating condition, no air leaks, good compression etc.
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Ewan
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10/25/2019 2:24pm
I run a rad valve, 38mm PWK Air Striker and PC exhaust / Silencer with mine. It’s stock bore and stroke, with mild porting.

Can’t vouch for the V Force. The rad valve has been on since I was 16, i’m 42 now 😂

Has always ran crisp and pulls well.
1
Banana_oil
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10/26/2019 11:34am
A friend compared oem with rad valve on a 90s cr125 in dyno. He lost 4hp with the rad valve 😁.
KHI Guy
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Cleveland, OH US
10/26/2019 1:09pm
Nice looking bike. Was that bike listed locally? If so, I obviously missed it Angry

I always go with Boyesen for all my reed needs.
sandman768
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10/26/2019 6:48pm
Banana_oil wrote:
A friend compared oem with rad valve on a 90s cr125 in dyno. He lost 4hp with the rad valve 😁.
Post up your friends dyno results.....
2
Banana_oil
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10/27/2019 1:28am
Banana_oil wrote:
A friend compared oem with rad valve on a 90s cr125 in dyno. He lost 4hp with the rad valve 😁.
sandman768 wrote:
Post up your friends dyno results.....
Sorry, don't have them but the tests were done by VHS so I trust the results.
1
nkoebes826
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North Canton, OH US
10/27/2019 6:30am Edited Date/Time 10/27/2019 6:49am
nkoebes826 wrote:
Thanks sandman. The rad valve is what ive been leaning towards but still not totally sure yet. Do you see a power gain at all with...
Thanks sandman. The rad valve is what ive been leaning towards but still not totally sure yet. Do you see a power gain at all with the rad valve or does it still seem relativity the same as stock? Also on some other fourms people were saying they had to lean out the pilot jet to get their bikes to run right with a rad valve. Have you had that experience or does it seem to run fine right after you install it?
sandman768 wrote:
I have used both vforce and rad valves on different bikes, they are both quality products and good replacement choices. I feel the power characteristics vary...
I have used both vforce and rad valves on different bikes, they are both quality products and good replacement choices. I feel the power characteristics vary from model to model. Hard to say how each one would work on your particular bike. Do not expect massive power gains from either, but proper functioning reeds are essential to your bike running properly. I would start with standard jetting and do some plug chop runs...Pro Circuit and FMF have jetting specs for a lot of the older models, that is also a good starting point. As with all jetting, so many variables it is impossible to just say what will be needed. On my older bikes, where parts are scarce & pricey, Error on the rich side then work my way leaner as needed. Verify what jets are currently in the carb, compare with factory settings, brings some spare pilots & mains in both directions, and go out for a test session, it does not take very long to swap jets on a 2t. Of course this is all assuming the engine is in good operating condition, no air leaks, good compression etc.
The bike was jetted extremely rich when I bought it. Before i started tearing the kx down to rebuild it I put pro circuits recommended jetting in it just out of curiosity and it cleaned it up a lot. I'm going to go through the motor and whole bike this winter so we will hopefully eliminate most of the variables.

SLOWTIME sent me some awesome info from Eric Gorr on his recommendations on a 90-91 kx125. He says the best value modicafition for this bike ironically is a boysen rad valve. His recommendations on jetting is air screw out 1.5 turns, stock pilot jet, stock or one size bigger main jet, a slide out of a 1990 kx125 or kdx200 (CA6 slide) and N84C needle. So needless to say that'll be the set up im going to try and we will see how it works out.
1
nkoebes826
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North Canton, OH US
10/27/2019 6:45am
KHI Guy wrote:
Nice looking bike. Was that bike listed locally? If so, I obviously missed it Angry

I always go with Boyesen for all my reed needs.
Thanks, it wasn't local to me. It popped up on fb marketplace and I drove about 6 hours to New York to get it. I couldn't pass it up, I love these early 90s 125's. It is a very clean base to start from, the bike defently had a very easy life. All the plastic is oem besides the fork guards, and it has period correct pro circuit pipe and silencer so just those 2 things made me not be able to pass it up. It has a few kinks like every bike you buy but nothing that cant be fixed. Who ever had it liked going to Lowe's to buy bolts for it sadly but if that's the worst thing I come across I'm stoked. Hopefully when this bike build gets finished up I'll take it to a few vet nationals to have some fun on it.
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