Does RB mod help with spoo?

Questions and Answers about the best carb and Head mods available for the KDX.
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wanaride
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Does RB mod help with spoo?

Post by wanaride »

I'm curious if anyone who has the RB carb mod has noticed a change in spoo coming out the spark arrestor after the mod was done.
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Post by m0rie »

Did you have ron modify your stock carb or get and airstryker?
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Post by wanaride »

Neither yet.
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Post by m0rie »

I actually noticed that my spooging pretty much diminished after switching to an RB modded carby. I think that has less to do with the carb itself and more with having pretty spot on jetting. A couple of people with the Airstrykers noted that they had an increase in spoo production. I certainly wouldn't let spoo or the lack thereof stop you from getting it, there is a noticeable difference.
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Post by Indawoods »

Jetting tends to go to the leaner side when getting RB'd.
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Post by Jeb »

I get a little spoo - I find a few splatter drops on the fender/swingarm - but that existed prior to RB mods (it seemed to increase a tad after I installed Boyesens believe it or not).

So I did not see an increase in spoo AFTER the RB mods
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Post by wanaride »

Thanks guys. The reason for the question...I suspect (hope) Ron Black can get the jetting closer to "spot on" than I can.

I changed my silencer packing this week and I thought I had found an untapped oil field inside my S/A. I'm surprised my bike isn't drowning from all of the oil that is likely in the expansion chamber.

A local mechanic told me that all 2Ts spoo. That makes sense to me. However, my son's KTM 50 doesn't spoo and a friend's KX250 doesn't spoo, yet my rear rotor is turning gray from the spoo. My bike doesn't foul plugs, but it makes lots of spoo. I wonder if the KDX motor just doesn't get hot enough to vaporize its fuel? I have had my jetting very lean and very rich, tried different premix brands and ratios, and the spoo was always there.

The RB mod is the last one on my list, so maybe it is time to get it done and see how it goes
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Post by paceyman »

"The RB mod is the last one on my list, so maybe it is time to get it done and see how it goes"

Did you get the RB mod done and did it take care of your slooge problem?

I have the exact same problem and wanted to see what happened.
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Post by Indawoods »

Ron's carb mod will not solve your spoo problem. My bike actually spoo's more after the mod. But this has nothing to do with Ron's work. It has to do with your jetting, how you ride, mixture etc.

Definately get the carb mod but don't expect it to solve the spoo issue. And Ron can get the jetting close but don't expect Ron to jet it for you... that's up to you.
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Post by fuzzy »

What oil are you using? Just about all castor blends will spoo, when used in a woods application.
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Post by skipro3 »

I'm of the opinion that a large percentage of spoo is unburned gas and not the 2 stroke oil going unburned. It was explained to me some time ago and I can't recall the details though.

Jetting for spoo, or lack there of, is not the way to go. Jet for a plug reading and then for seat-of-pants performance. The plug read so as not to destroy the motor, and s-o-p because that is the true test. I've heard of folks jetting and changing jetting by modifying their oil. Add more oil to your two-stroke fuel mix and you lean out the gasoline and the bike will run leaner. Cut back on the oil, say, from 32:1 to 50:1 and you make the bike run richer. If cutting the mix from 32 over to 50:1 and not changing any jets causes more spoo, then it's pretty clear the spoo is unburned gas and not oil. I discovered this. If you are going to change your oil by brand or amount, then you need to change your jetting accordingly. Think about this and see if it makes any sense to you.

And another thing: Gas can NOT burn unless it's vaporized. Micro-droplets of gas, suspended in air is NOT vapor and it will NOT burn. In order to get the micro droplets of gas/oil to a vapor, they are heated and swirled around in the ports and head area of your cylinder. Then, when the piston comes up to compress the mix, it squishes it in a pattern that, when an ignition source is introduced, will burn in an even pattern and completely. Poor vaporization, poor mixing, bad design of squish band on the cylinder head all affect how much of the fuel is converted to vapor and burned. That's one reason I'm not big on polished ports; it deminishes the turbulence of the fuel with the air and the dropletts of fuel do not vaporize as well. Sure, you get a big dose of fuel mix because it gets to the combustion chamber more efficantly, but it's still in droplet form and can't ignite until it's a vapor.
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Post by fuzzy »

Vince....I swear we get that due to the gasohol! Well, that and not COMPLETELY ANALLY tuning.
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Post by paceyman »

What oil are you using? Just about all castor blends will spoo, when used in a woods application.

________________________________________________________________

I've been running Belray MC1 since I bought the bike last year.

Here is what it looks like after a couple of rides. Is this about the same as you all that have the spooge problem?

Image

Image

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Post by Indawoods »

Mine is not as bad as that... but I got my jetting at 38/150. I am wanting to go with a 148 main but I don't have one....

But, the plug looks beautiful as is....

It used to spoo worse at 40...so I am getting it purdy darn close and will have to start going back up as the weather gets cooler.
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Post by wanaride »

Yes, my spooge problem looks identical to yours. I've tried H1R, Maxima K2 and Amsoil Interceptor with any jetting combination and premix ratio you can imagine, and they ALL resulted in the same picture you have above. I've only fouled one plug in 4 years though.

I got tired of messing with the jetting so I picked some conservative numbers and left them there. (I don't even remember them now but I know I don't have a 40 pilot/150 main in it.) I don't have a large open area to ride in so a plug chop is out of the question. Maybe some day I'll try again, but I just got tired of taking the carb apart.

It is frustrating though when I see my son's KTM 50 silencer looking clean...
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Post by paceyman »

Yes, my spooge problem looks identical to yours. I've tried H1R, Maxima K2 and Amsoil Interceptor with any jetting combination and premix ratio you can imagine, and they ALL resulted in the same picture you have above. I've only fouled one plug in 4 years though.

I got tired of messing with the jetting so I picked some conservative numbers and left them there. (I don't even remember them now but I know I don't have a 40 pilot/150 main in it.) I don't have a large open area to ride in so a plug chop is out of the question. Maybe some day I'll try again, but I just got tired of taking the carb apart.

It is frustrating though when I see my son's KTM 50 silencer looking clean...
__________________________________________________________________________________________________________________________

Well, if you guys can't get this bike splooge free, then what chance does a rookie have? :? :? :?

I have the same frustration when I am at a hare scramble race and see all the 2 stroke pumkins splewing smoke at the line and after 2 hours of racing see no drips out the silencer. My roost protector and Camelback are covered with black.

I e-mailed James Dean about my jetting. He has some suggestions as well that I will try later in the year. There is about 1.5" of oil left in my gallon jug of MC-1 and when it's gone - it's GONE!!! :cool:

Either way I will post what I did and provide the results here.

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Post by skipro3 »

I'm still saying that the spoo is not the 2 stroke oil from your fuel. There's just too much! Considering how much is on the bike, imagine how much was blown away from the bike and is on the ground somewhere. I imagine it would be more than the 2.4oz per gallon of gas that you burn (50:1 ratio). So, if you agree that you are likely to be spooing more than 2 or 3 oz per gallon burned, then the spoo is not the oil, but instead is gas residue that looks oily.

Remember also, change in jetting, fuel or oil isn't going to affect spoo immediately. There is the residual left in the silencer/spark arrester as well as down in the pipe itself. It could take several rides to blow it all out.

I've had my bikes jetted correctly and using pump gas, had TONS of spoo. Then I went to race gas, specifically VP Racing's C-12, and the spoo was completely gone. Started with a fresh repack on the S/A and cleaned the pipe. After 100 gallons of fuel, the S/A was unpacked. It had a gray tinge to it like it was held over a campfire and picked up the smoke color.

My recommendation to anyone really interested in getting rid of spoo is to first, not waste time with different 2 stroke oils thinking one burns clean. All the synthetics are clean burning. That is what they are designed to do. Even my outboard motor 2 stroke oil is specifically smokeless. Second, jet the bike correctly by plug reads. Jet all circuits, not just the main, for optimum performance. Third, try going to a race gas. C-12 will completely vaporize at the temperatures and time window the KDX provides. Just remember that since C-12 is going to completely evaporate, unlike pump gas, your jetting is going to be richer and you will need to re-jet to a leaner amount with the race gas.

Side Note: I took a sample of C-12 and one of pump gas and put several drops of each in separate clear glass containers. I let them evaporate and then observed the glass. The C-12 glass had zero residue and zero odor. I could have put the glass back in the kitchen cupboard. The pump gas had a good bit of residue left in the glass and a strong gasoline odor. It also took a lot longer to evaporate. You might try a different brand of pump gas. Perhaps the one you use is of a formula that has additives that affect your exhaust spoo.

But hey, if you want to try and clear your spoo problem by jetting and oil brand swapping, go ahead. Let us know how it works for you. Just don't say you weren't told about the probability that it's the gasoline you use.
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Post by Indawoods »

We really need to get to the bottom of this spoo issue. I have no idea where I would get C-12 around here but it is worth a look....
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Post by skipro3 »

I'll check, but around here, just about any of the dirt bike shops carry it. I recall checking their website, finding the local rep and talking to him for quite a while about which gas I should use. Keep in mind that he recommended C-12 because I had RB do my head for race gas and I ride trails, not MX tracks. Eventually I mixed the C-12 50/50 with premium pump gas; Union 76. I was told that the Union76 gas had less issues with consistency. Straight C-12 didn't provide me as much power as premium pump gas either. Go figure!! But again, I wasn't looking for more power, I wanted crisp and sharp jetting. I've had plenty of riders try my modded KDX220 and they were amazed at the bike's snappiness. 4th gear power wheelies were no problem and yet the power hit was non-existent. Very linear except from the very bottom end where it was a bit explosive. I needed to be one gear tall when going slow.
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Post by Jeb »

>|<>QBB<
Indawoods wrote:We really need to get to the bottom of this spoo issue. I have no idea where I would get C-12 around here but it is worth a look....
http://vpracingfuels.com/index2.html

Click on "VP Distribution Centers" and drill down to your region for contact info. Then call this week and find out where to find the C-12
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