That UH-OH smell! ( long)

CC_RIDER

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#1
I'm having a tuning nightmare. My local KTM dealer keeps changing racing fuels. Up until a month ago I had been using Superfast and was running strong and smooth, then he changed to VP (12). I started running a little too rich so I rejetted. Now he has changed again, to Trick. So I bought a new plug and headed out to do some testing.

I noticed a marked improvement in my response from off idle, but then it started four stroking with little surges. When it finally got on the pipe, there was a definite miss and did'nt seem to rev out all the way.

All the above was in about a quarter mile pass. I turned around to do another run back the other direction, and noticed a strong smell like something burnt, in the air. Well I was cranked to full throttle before I realized that smell had come from my bike. I was smelling the exhaust from the first pass.

This was a smell I had smelled before, like an engine that had been run dry of oil. Visions of black and blue bearings and races ran thru my head.

I immediately shut it down and coasted to a stop. I first checked the engine, and it did'nt seem any hotter to the touch than usual.
I did notice a line of white smoke filtering from the silencer, and a thin runny spooge dripping from the spout.

I pulled my plug, and it looked about right, and was not too hot to hold.
I then cranked the engine thru by hand to see if it was trying to seize, but it cycled fine. I did notice a sizeable puff of white smoke from the silencer, so I checked that out again.

The smell was definitely coming from the pipe/silencer. There was more spooge than I had ever seen. It was all over the back tire and rim, and was slung from there all over the underside of the fender and along the swingarm.

As I said earlier, I had been running a little too rich and had noticed a thick dark spooge that would run down the side of the silencer spout.
But this was excessive spooge, and much thinner in consistency.

Where I ride, I don't get to really "blow it out" much.
Could it be that running at full throttle was just burning and blowing out all the accumulated spooge in my pipe and silencer?
Would it cause that burnt bearing smell?
Could it just be the way the Trick fuel smells?

This incident really scared me.
I put my plug back in and road back to the house very slowly. The bike seems to be fine, however I will give it a good check up tomorrow. I did notice that the inside of the silencer looked like it had been surgically cleaned! Before I left this afternoon it was black and sooty.

Has anyone here had any experiences like this? What were the results.

Here are my specs:
'97 250 SX
Trick mixed 40-1 Bel-Ray MC-1
NGK BR8
#45 pilot
# 170 main
N85D needle, clip in middle
air screw 1 1/2 turns out
altitude 850 ft.
temp 92 degrees.
running on flat pavement.

Would this jetting/fuel combo fry my engine?

Please respond if you have ANY thoughts on this.

Thanks.
 

marcusgunby

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#2
Sounds to me like you bike got a good clear out,if the plug looked good after a full throttle run then you will be o.k.
 
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#3
Where are you buying the fuel? If it is the dealer I use, I don't buy fuel there anymore. I only bought it 2 times and was not impressed. It was 99 octane, I can get B32 110 for the same price. I cut it with super unlead pump 2:1, and it works just as well.
 

CC_RIDER

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#4
Marcusgunby, thanks for your input. I need all the positive support I can get after that experience. :confused:


Scott, I buy my fuel from DFW KTM.

This was fresh fuel. (they had just opened the barrel)

Actually I was not impressed with VP, but I was satisfied with the Superfast.

The jury is still out on the TRICK. My first impression was not good. That may change after I get my jetting dialed in. It's supposed to be pretty good. They tell me it is what Carmichael uses. I don't know about that, I'd just be happy if my dealer would stick with one brand.
 
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#5
one of my friends had a similar problem, his bike fell off of the stand and his gas was on so the next day we went to go riding and he saw what happenes. We picked it up and filled it with gas and than started. It took a few kicks but once it started running it ran like crap missing like your bike did and than all of a sudden spooge was coming out like crazy, i mean it shot out all over it was on everything. The conclusion we came to was that the gas ran through the bike since it was on and got into the pipe and was in the cylinder and everywhere, but the bike cleared out and ran fine after
 
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#6
The only time I heard of a pipe filling up with gas was from a ktm owner. He told some weird story of how the exhuast pipe would fill up with gas if the valve was left on. This didn't make any sense, and it was one of those "smile and nod" things. Coincidence that it was also a ktm, but I still fail to see how this could happen...wouldn't it fill up the crankcase first?
 

CC_RIDER

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#7
Well, I think my problem was an excess build up of spooge in the pipe, not raw fuel.

I rejetted back to stock, except I dropped the needle down a notch.

I rode it hard for 1 1/2 hrs and it ran really well, with good response and power. It would bog a bit if I lugged the engine while slowing for hairpin 180 turns. I'm not sure if that is due to a rich condition or lean. I'll play with the air screw next ride and see if I can find the sweet spot.

I'm just really relieved that no apparant damage has been done.
 
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#10
I find this very same thing on my buddies KDX200. He rides slow for a while in the woods and then rides down the street. It heats the pipe up and creates a horrible smell and tons of white/blue smoke. As it is air cooled it is not water. We at first thought the engine was giving up the ghost. In reality it was just burning out the garbage in the expansion chamber.

Chris