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Smoking (exhaust) at higher speeds?

Sceep

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I have never owned a 2t before I got a trials bike. I am on my 4th trials bike now and all 4 of them have displayed this behavior.

80:1 Redline premix in 100 octane e-free fuel.

Bikes are virtually smokeless in sections, or on short loops. But somewhere like out trail-riding with a long connector between trails, a mile or more wound out in top gear, they smoke BAD. Like, people behind me are asking "WTF is wrong with your bike?" .

Happened with the new Beta Sunday when riding back from my practice area down the road. Roughly 0.4 miles wound out in 6th. When I pulled into the garage it instantly clouded the place out.

What am I doing wrong? :dunno
 

Knobbytracks

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You need to occasionally rev that thing out! :ricky
Trials bikes are ridden at such a low rpm that the exhaust packing absorbs the unburnt exhaust emissions. When you high-tail it down a road or for extended periods, the smoke you and your buds behind you are experiencing is that build-up getting burned out.
 
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YmirTrials

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You need to occasionally rev that thing out! :ricky
Trials bikes are ridden at such a low rpm that the exhaust packing absorbs the unburnt exhaust emissions. When you high-tail it down a road or for extended periods, the smoke you and your buds behind you are experiencing is that build-up getting burned out.
What he said, I think everyone has this same experience.
 

Yinzer Moto

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I have had my exhaust actually catch fire. It usually happens when I go out to the UTE cup, and on the first big climb. I will occasionally get here on the east coast, when the loop has a long climb.
 

fprintf

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I sometimes most enjoy the long hillclimbs we get that let me burn the oil out from the exhaust. You know when you get to the top of the hill and it is just smokey as all heck and everyone behind you is complaining that you've done a good job.

Although I found on my last bike once I took the exhaust off that despite such periodic cleaning out that it was still completely loaded with oil and surprisingly water. Putting a propane torch to it did wonders to clean it out (just before I sold it, it turns out).
 

matty

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This tends to be commonplace and is for precisely the reasons others mention above.
It could be reduced perhaps by a change of oil, perhaps one with a lower flash point might help in that it might burn largely unnoticed internally before a big build up with eventual ignition as mentioned by yinser . try swaping out the redline for say motul 2t save the money and who knows it might just cause less smoking.
 

fprintf

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motul 2t save the money and who knows it might just cause less smoking.

That is what we run mostly around here. Motul 710 2T because it has a rather low flashpoint and tends to burn out reasonably quickly.
 

Buschog

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Friend melted the tip out of her 2019 TRS One R 300 at the British American Cup last weekend. It was a fun, long loop, that had been used for a hare scramble. Tons of up and down, and some long flat out stretches. Don't know what oil she runs. I use Motul 710 and didn't have any significant smoking, but I only have 20 hours or so on my 2022 250 One R.

I didn't melt anything, but I did pinch flat my front tire about 4 miles out. I rode 2 sections that way ( 3 & 5 ) and all the way back to the pits. 4ish miles of off-camber on a flat front sucks.
 

Yinzer Moto

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Friend melted the tip out of her 2019 TRS One R 300 at the British American Cup last weekend. It was a fun, long loop, that had been used for a hare scramble. Tons of up and down, and some long flat out stretches. Don't know what oil she runs. I use Motul 710 and didn't have any significant smoking, but I only have 20 hours or so on my 2022 250 One R.

I didn't melt anything, but I did pinch flat my front tire about 4 miles out. I rode 2 sections that way ( 3 & 5 ) and all the way back to the pits. 4ish miles of off-camber on a flat front sucks.

You guys run spark arrestors? Was her‘s starting clog? I saw one really melted TRS end cap at the UTE cup this past year.
 

Buschog

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You guys run spark arrestors? Was her‘s starting clog? I saw one really melted TRS end cap at the UTE cup this past year.
Didn't think of that. Yes we have to run SAs at all times. I'm not sure if hers was clogged ot not, but that would definitely contribute.
 

YmirTrials

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Would the spark arrestor get clogged up in a smoking silencer situation or might it get ‘burned’ out too? Guess it depends how hot the pipe gets? :scratch
 

Buschog

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Would the spark arrestor get clogged up in a smoking silencer situation or might it get ‘burned’ out too? Guess it depends how hot the pipe gets? :scratch
Another friend, at The Ute Cup last year had his SA clog so bad it was causing his engine to run poorly and I think stalled it a couple times on his way back to the pits. Come to think of it, I think it was on the same bike as above ( 'he' sold it to 'her' ). He pulled the SA in the pits and cleaned it with brake clean. It was so hot it ignited and set the grass on fire. I had to get the extinguisher out of my camper.
 

YmirTrials

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Another friend, at The Ute Cup last year had his SA clog so bad it was causing his engine to run poorly and I think stalled it a couple times on his way back to the pits. Come to think of it, I think it was on the same bike as above ( 'he' sold it to 'her' ). He pulled the SA in the pits and cleaned it with brake clean. It was so hot it ignited and set the grass on fire. I had to get the extinguisher out of my camper.
That sounds like a ‘don’t try this at home’ moment! :photog
 

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