Jetting using another carb

[bigt94550]

I have been trying to get my bike to stop spooging. Yes I have the finicky 01 CR 250. My brother in law has the same bike and his runs crisp with no spooge. Can I use his carb set up and expect the same results or does each engine have its own "signature" and need to be jetted accordingly?
I'm getting tired of taking this thing apart and going through the jetting steps. I just want to ride spooge free.
Thanks,
Troy

 

[TimberPig]

Each engine will require slight changes, due to differences in compression,carburetion, head design and porting. The production tolerances do not make each part exactly the same, so there is some variability.

That said, the differences are normally small enough that a setup for one will be close for another, ridden in the same conditions by an equal rider. If he rides his bike harder or in different conditions than you, his jetting needs may vary from yours. If your riding conditions are the same, and the demands you place on the bike are similar, his carb setup should provide you with a good starting point.

 

[adam728]

Exactly what that guy said.


This is also assuming your bikes are setup the same, such as same exhaust, reeds, etc.

 

[KX250Dad]

Might also consider re-packing the siliencer, the fibers coalesce oil mists to droplets over time and when saturated/carboned the droplets form and simply pass out the end. Also, if you feel it a jetting issue is there any froth/spooge coming out the pv vent or an occassional puffing of vapor/smoke... this might point you in the right direction.

 

[rmc_olderthandirt]

My brother in law has the same bike and his runs crisp with no spooge.

Do you use the same oil and mix ratio as your brother-in-law?
Do you both weigh the same?
Do you shift at the same point, push the bike equally hard?
Are you both running the exact same sparkplug?
Do you clean out and repack your silencer as often as he does?

A "no" to any of those, and probably some questions I didn't think to ask will make the results incomparable.

A two stroke has oil in the gas. This oil usually doesn't get burned completely and is expelled out the exhaust. When it leaves the cylinder it might be in a vapor but as the gases cool in the pipe the oil can condense out and end up collecting in the pipe and silencer.

Making the engine work harder, either from carrying a heavier load or simply pushing it harder will increase the temperature of the cylinder and exhaust system. A hotter pipe will tend to keep the oil as a vapor and expel it instead of letting it condense.

A hotter spark plug will burn the oil deposits off more easily, making the bike more crisp.

Taking your silencer off, cleaning it out and replacing the oil soaked packing with fresh packing will make a big difference, for a while. It will most likely get saturated again but for a while it will be better.

Rod

 

[bigt94550]

For the most part the bikes are identical. Fatty pipe, vforce reeds, FMF silencer, same mix.
I ride harder, he's a little heavier.
I was thinking about putting his carb on my bike and trying it out, to see if it would correct my problem; but I am a bit afraid of a too lean condition (if the change was too drastic) and screw up the motor.
Thanks for the input everyone,
Troy

 

[cr125freak]

i would just try it. As in main pilot and needle. If its close then dial it in. Make sure you have fresh packing or jetting is useless

 

[uts]

i would just try it. As in main pilot and needle. If its close then dial it in. Make sure you have fresh packing or jetting is useless

How does the silencer packing effect the jetting? Not being smart I just don't understand. I realize that if it's full of spooge, it will still spooge even if you get the jetting right, but how does it effect the jetting changes as far as performance of engine?

 

[TimberPig]

How does the silencer packing effect the jetting? Not being smart I just don't understand. I realize that if it's full of spooge, it will still spooge even if you get the jetting right, but how does it effect the jetting changes as far as performance of engine?

Old worn out, oil soaked silencer packing will increase the turbulence and reduce the flow through the silencer. By restricting the exit of exhaust, you make the bike act more rich. The turbulence isn't consistent and will vary as the packing deteriorates further. By using fresh packing, you reduce the effects of worn out packing on the flow of exhaust, and allow the bike to be tuned correctly, rather than fighting with other issues besides the jetting needs of the bike.

 

[bigt94550]

Update...My bike has: 400 main, s7 nozzle, 25 slow jet and 1-76 needle in the 3rd position.

Brother in law: 420, s9, 30 slow, 2-74 1st position.

His seems so mich richer by the numbers, but runs clean. Why?

As I said, same mix and riding conditions.

I did repack the silencer and it was nasty black and gunky, but haven't had a chance to ride it yet.

Some one earlier recommended an s4 nozzle, but their post is gone.

If that doesn't work I might just go the carb swap route. Is AJ still the one to speak to at Service Honda?
Thanks for the help and ideas, all,
Troy