2005 CR125 chassis and carb with 2003 CR125 engine...HELP

billyg371
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billyg371
Edited Date/Time 4/28/2016 2:35pm
Hey guys need some help here.
I have a friend who bought this bike for his son and really wasn't aware of the issues. Heres a quick overview

The frame, wire harness and Carb is a 2005. The engine is a 2002-2003. Had a hard time finding the right cylinder to match the bottom end.
The issue lies in the mixture and jetting. The bike will foul out BR8ES plugs within 10 minutes of riding. The mixture he had to run to eliminate that had to be changed to 50:1 (VERY LEAN) Also switched to a BR7ES. Jetting is 410 main, 50 pilot and 2 on the air screw.
Heres where it gets a little weird... Pulled the plug out today and it is soaked. Oil still spitting out of the exhaust and covering the swingarm fender and brake caliper. The bike has absolutely no bottom end whatsoever. Also running 13-52 gearing. Whole engine top and bottom have 6 hours on it.

Im not sure where to even start on this thing. His son races hare scrambles in the B class would like to be somewhat competitive. He already dumped a ton of money into suspension, tank and rebuilding the engine (nightmare) so I'm just looking to help him out with getting this thing running somewhat decent so he can finish out the season on this bike.

If anyone can shed some insight into this it will be much appreciated.
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Tracktor
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Tracktor 4/27/2016 9:43am
4/27/2016 9:43am
In changing to 50:1 you actually richened the jetting. As someone who has experience with these CR's the first thing I would recommend is putting a 38mm Keihin Airstriker carb on it. Much simpler to jet & more consistent. Mix 40:1 and start changing jets from there.................
Paw Paw 271
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Paw Paw 271 4/27/2016 9:51am
4/27/2016 9:51am Edited Date/Time 4/27/2016 10:04am
The OEM jetting should be 32:1 for this bike. At 50:1 you have increased the gas part of the mixture way too much.
When the engine was rebuilt, were new crank seals installed?
Was the carb float height set correctly?
Is the float needle sealing correctly?
Are you sure the exhaust valves are working correctly?
When you out the engine together did you check the squish? ( Sounds like you may have a miss match of parts)
Did you do a compression test?
A leak test?
Paw Paw
pete24
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pete24 4/27/2016 10:53am
4/27/2016 10:53am
ok i have had a number of cr 125s that foul plugs no matter what you do,inn the carb where the float needle sits is a pressed in brass spinelli, it has an oring on it that you cant buy, and gas is leaking rite past it at an alarming rate, luckily the whole needle seat costs like six bucks here is the part number 16012-KZ4-A92
billyg371
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billyg371 4/27/2016 11:09am
4/27/2016 11:09am
Paw Paw 271 wrote:
The OEM jetting should be 32:1 for this bike. At 50:1 you have increased the gas part of the mixture way too much. When the engine...
The OEM jetting should be 32:1 for this bike. At 50:1 you have increased the gas part of the mixture way too much.
When the engine was rebuilt, were new crank seals installed?
Was the carb float height set correctly?
Is the float needle sealing correctly?
Are you sure the exhaust valves are working correctly?
When you out the engine together did you check the squish? ( Sounds like you may have a miss match of parts)
Did you do a compression test?
A leak test?
Paw Paw
Yes that is correct on the 32:1. engine was rebuilt with new crank seals (i did not rebuild it)
float is in spec
needle and seat are new and sealing perfect.
i will be checking the exhaust valves after work.
i would hope that the engine builder checked the squish.
the complete engine is an 03
compression is good
leak test was also good
Im going to mess with the jetting tonight, repack muffler and check the powervalve. if that doesnt work ill be getting the pwk carb.

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Hondas4Life3
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Hondas4Life3 4/28/2016 7:53am
4/28/2016 7:53am Edited Date/Time 4/28/2016 8:39am
Do a Leak down test first. The 03 engine is a completely different design with the power valve. I would start with putting on a complete 03 ignition system. CDI, harness, etc. 32:I with bleray H1r and 93 pump gas... I was running a 400 main and i think a 47.5 or 50 pilot on my 05 cr125 Do not put a 7 heat range plug in it stick with br8eix or br8es. If it was mine i would put a 03 carb on it as well so the TPS will hook up and jetting will be easier to get a baseline.
rallendude
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rallendude 4/28/2016 8:24am
4/28/2016 8:24am
Oil spitting out the exhaust and soaking the swingarm isn't usually jetting. Check the right side crank seal.
RyanLester761
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RyanLester761 4/28/2016 10:32am
4/28/2016 10:32am
rallendude wrote:
Oil spitting out the exhaust and soaking the swingarm isn't usually jetting. Check the right side crank seal.
Ding ding ding!!!

I had a 2001 CR125 which had the drooling and smoking issue too. It turned out the right side main seal had pushed out and it was sucking tranny oil into the crankcase. Luckily, they are easy enough to replace.
billyg371
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billyg371 4/28/2016 12:10pm
4/28/2016 12:10pm
rallendude wrote:
Oil spitting out the exhaust and soaking the swingarm isn't usually jetting. Check the right side crank seal.
RyanLester761 wrote:
Ding ding ding!!! I had a 2001 CR125 which had the drooling and smoking issue too. It turned out the right side main seal had pushed...
Ding ding ding!!!

I had a 2001 CR125 which had the drooling and smoking issue too. It turned out the right side main seal had pushed out and it was sucking tranny oil into the crankcase. Luckily, they are easy enough to replace.
Crank seals check and there is no leakage. now the powervalve and head are a different story. I guess the head was never replaced when the guy rebuilt it so i ordered a new top end kit, head, and some power valve parts. im not too familiar with the power valve. i referred to the service manual and that was terrible. does anyone know if the 03 has a bearing where the shaft goes through? It looked like the powervalve wasnt working properly.
RyanLester761
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RyanLester761 4/28/2016 12:40pm
4/28/2016 12:40pm Edited Date/Time 4/28/2016 12:43pm
Good to know the main seal is good.

I looked at motosport.com's site and part #16 is not noted so I can't tell if it's a seal or bearing. (link below)

http://www.motosport.com/dirtbike/oem-parts/honda/2003/cr125/exhaust-va…

Also, did you say the head looks bad? Do you think it has a blown head gasket? You said the leakdown test was good. Would it hold pressure/vacuum if it had a leak into the cooling system? (I'm curious for my own knowledge) I would imagine the cooling system would be under a ton of pressure and somewhat blow the cap off if you loosened it immediately after running.

Another thing: My buddy (assumed he) had a broken carb on his '97 yz250. He went through the carb several times and there was no visible cracks but the only remedy was a new carb. You might be on the right track...
RyanLester761
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RyanLester761 4/28/2016 12:48pm
4/28/2016 12:48pm
I'm trying to help, and I want to know myself. I found a picture on ebay of a 2000 cylinder. It appears to have a bearing. I assume the 2002-03 also use a bearing.



Paw Paw 271
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Paw Paw 271 4/28/2016 2:04pm
4/28/2016 2:04pm
The 2003 does have a bearing , but as previously stated it is not a part you can order off the shelf. You may have some luck with removing it and taking it to a place like Bearing Services to find a replacement.
That bearing, even if bad should not keep the valves from opening. I would think the linkage or the governor may be the issue. ( but none of these would cause the oil issue this started with.
You said you did a compression and leak test....What were the readings on these test?
I am still leaning towards a bad crank seal on the clutch side.

Paw Paw
billyg371
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billyg371 4/28/2016 2:35pm
4/28/2016 2:35pm
the bike is basically a frankenbike haha. ill check the readings when i get home from work. i wrote them down. the compression i remember was 150-155. leak down ill have to check. I was shocked that it had 150psi when i took the head off. pitted and looked like some shot a bb gun at it. Come to find out the guy who rebuilt it put that crappy pitted head on it with a new jug, and top end kit. As far as the power valve.... almost positive there isnt a bearing in it..So im attempting to help my friend out so his son can finish up the season while i fix all of the other guys mistakes and oh i just give up on that problems.

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