2 stroke exhaust coke

[Arfdog]

Performance on my rxs100 has been getting rapidly worse over the last two days, the first 2 days that I've been riding it. I've posted threads about it possibly being an over-oiled air filter.

When I came home today, I struggled to get her over 30mph. I almost got killed by an idiot overtaking on the inside when trying to merge onto a large road. depressing really on my first proper day on my bike.

When I got home, I re-checked the exhaust, which was black but not gunked up the last time I checked it (2 days before). This time there were about 10 potato chip thin bits of gunk down the middle of it, about the size of 20p coins. I gave the exhaust a bashing on the ground, and they came out. Other than that, the exhaust only has a coating of blackness.

Do you think this would be enough to account for the crap performance? Anyone got a pic of what a totally gunked exhaust looks like? Thanks.

it might be worth adding that it's been standing for 18 months up till now, so my riding possibly loosened some gunk hence rapid deterioration in performance. Can't test ride bike now, waiting for new air filter.

[Jebus]

Well it depends on the bike but have you checked the plug air filter and everything else are ok? if its been sat a long time with fuel in the tank it may of gone off a bit so wont burn as well, a good way to get the coke out is 2 run it for a decent amount of time and a good high revs blast, you could try redex but not sure if thats ok to use with a 2 stroke engine.
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2nd time around CBT: 8/9/11
125 Varadero

[fuzz]

[Pete.]

[Jebus]

yeah thats the proper way of doing it and you end up with a very nice sparkley clean exhaust, give it a go it should help a bit even if the problem is not so serious
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2nd time around CBT: 8/9/11
125 Varadero

[Arfdog]

Thanks All.

I will most defintitely try the caustic soda approach, as well as further investigate the redex idea. Can't wait to get back on the road with a bike I can trust to maintain the speed limit with ease...

[fuzz]

[Trixie]

Deffo caustic soda.

Just don't do what a mate of mine did. He slooshed the silencer out with petrol, emptied it and had a good look up there. When he decided it was too dark to see anything, he thought he'd strike a match so he could see better....

....singed eyebrows and hair later, the rest is history. I p'd myself laughing when he told me - because I knew he was OK, but it could have been so much worse....
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Dead nobodies in company cars...

[Arfdog]

Three more things: with caustic sode, is it necessary to put the entire exhaust in a bin full of water? I have no bin that large.
I am pretty sure the exhaust has no leaks though, it is in very good condition.

Also, I take I have to leave the silencer bit inside, bolted in as usual. I will remove it after the caustic'ing, when getting all the newly unstuck junk out?

I have been told a potato makes a good plug for the cylinder end of the exhaust, do you reckon a potato has the necessary chemical integrity to hold true?

I'm about to go walk around the car parks outside, to see if I can spot the white vectra that attempted to murder me yesterday. I dreamt about meeting the driver last night, and it was not a sexy dream by any means.

[Pete.]

[Arfdog]

I imagine chemists might be a little more careful nowadays when it comes to any chemicals which could conceivably be used in bombs or so forth. I did find some at B+Q though. Maybe there are differing grades?

[Pete.]

[Serendipity]

Hi Arfdog, before you set off on a project to melt your hands etc have you eliminated other possible causes? I suspect that if you can still easily remove the baffle from your RXS exhaust you may not be suffering from too much coking.

My current RXS has stood unused for longer periods than 18 months and still been ok with a drop of fresh fuel and a battery charge. The last time I really had trouble with difficult starting and poor running it was just a shagged spark plug. Even if you replaced the plug recently it’s possible it’s got all oiled up. Have you got a new one you can try? Should be a BR8HS (or BR8HIX if you wanna spend the extra)

Looking at your other posts I thought I’d leave some info on my RXS in case it’s any help. I’ve had this one for nine years and although it’s only done about 6,000 miles in that time (it’s my spare bike) I’ve not yet felt the need for a de-coke of the top end or exhaust. Its mileage is around 23,000 now and it’s still performing pretty well. I’m not particularly gentle with it, but the engine will freely rev to the red line in most gears. Top gear at 6k rpm is 50mph and if you hit a hill or a head wind at that speed you may have to drop a gear. Mine will struggle up to about 72mph in favourable conditions before mechanical sympathy kicks in and I back off. Despite clever 1980’s technology the bike is still utterly gutless at lower revs. If you’re in too high a gear at 30mph it will take forever to speed up.

The air filter should only be slightly damp, not sodden with oil. However I seriously doubt that would have such a serious effect on your performance as to limit you to 30mph. I’ve not had problems with my carb, but is there a chance that you could have got water or rusty crud from the tank into yours? Have you checked the adjustment of the throttle cable at the handlebar, carb and oil pump?

Looking back over that lot it’s probably not much help, but feel free to ask any questions if you think I could help. All the best.
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[hazza]

try taking the baffle out of your exhaust and see if that improves the situation (it is very very loud with no baffle). at least then you can rule that out as a possible cause.
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3 Honda NC50's(Sold)-->'72 Puch Maxi S (Sold, want it back!)--> '90 Yamaha RXS 100 (Stolen)--> '87 Honda Cub 90(Sold) --> '95 Kawasaki Eliminator (Sold) --> '98 Bandit 600 (Sold) -->'07 SV650S (Current)

[Arfdog]

[Arfdog]

Serendipity, if I can ask one more thing:

The power band on your RXS, I imagine it starts around 5.5 - 6K like mine, but please tell me what happens at 7 - 9K. Is the engine still producing reasonable power all the way up to 9K, or does it drop off at any point?

Thanks.

[Serendipity]

OK, you’re probably right, that carbon could be the problem if it’s actually big enough chunks to block parts of the baffle.

Funnily enough I’ve owned 3 different RXS100’s with at least five exhausts between them and I have yet to see a baffle with the damping wool still in place. I guess all the previous owners have removed it or accidentally damaged it. However while it probably helps reduce the noise the wool has no effect on performance either way and I’ve never needed it in place for an MOT. I recall that the manual states that if you remove it the fuelling of the bike is unaffected.

Yup the power band on mine hits with a bit of a kick just before 6k (really annoying on cold wet greasy roads). I don’t know if the power is “reasonable” …. Maybe barely adequate would be a better term. Mine does produce fairly consistent power until just before the red line where it suddenly tails off with an “ohmygoditsgonnaseize!” feeling.

Have you experienced the bike going onto reserve on full throttle yet? If not that one will make you laugh. It’s like hitting a brick wall, repeatedly! No gentle loss of power to warn you here, just jerking violent enough to make you think twice about reaching for the reserve tap. And it always happens when you’ve just overtaken someone or got yourself in a vulnerable position. If you do manage to switch to reserve it still takes an agonising couple of seconds for the carb to refill before the power comes back. And if you come to a halt before the engine restarts prepare for much kicking to get the fuel back into the system.
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Arfdog]

mmmm, I've yet to get down to reserve tank, but next week I will, with a bit of luck! I have kicked and kicked, and kicked then realised I hadn't turned the tap on though... doh!

Lovely weather today, I hope it holds.
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I'm a lover, not a fighter.

[Arfdog]

Oh for feck sakes...

I removed the entire exhaust yesterday morning, and filled it with caustic soda dissolved in water. I left it all day long, then cleaned it up and hosed it out in the evening and put it back on the bike.

This morning, she ran like a dream! For about 5 miles, then I performance fell flat again. I removed the exhaust next to the road, and sure enough, it was jammed up with coke cornflakes!!!

So now what to do? It's not possible that the chips of carbon are coming from within the engine is it? All I can think to do is stop every 5 miles and empty the chips out of the baffle. What a drag...
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I'm a lover, not a fighter.

[Pete.]

You should be able to ratle some of it out of the front pipe. Looks like you've found your problem, just got to work on the cure.

[Jebus]

mabye the engine is really coked up? bung a load of redex thru it and give it a high revs blast, that will clean a load of carbon out, you may be over oiling, and this would make it run like a dog if you know how check the adjustment of your oil pump
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2nd time around CBT: 8/9/11
125 Varadero

[Arfdog]

Thanks guys, I chucked a tablespoons of redex down the sparkplug hole and left it for 30 mins, then started it up and gave it a burn down to the petrol station, filled up and added the right amount of redex to the petrol. I'll just ride it hard for a couple of days, and with a bit of luck it'll vomit up all the carbon. If I still get trouble, I think I'll find geri's chemist and get the terrorist caustic for the pipe, and remove the cylinder head to check if the piston is maybe a solid lump of charcoal...

In between the blockages, she goes beautifully! I'm very happy.
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I'm a lover, not a fighter.

[moonym20]

only flick read this thread, a mate of mine has a lovely RXS100 and we usaually decoke it on a regular basis,

on top of the the methods mentioned you wana remove your baffle as well (there should be a nut/lockwire at the end of the exhaust at the end underside. pop this off and then with two mole grips you next wana use one to clamp onto the baffle itself then use the other mole grip clip onto the first one (with me so far? lol) to create a lever arm, with the exhaust clamped in a vice (or still on the bike) you need to twist the baffle and pull slightly till she comes out, its likely to be a right bith till its out.

next we usaually take the removed baffle and set fire to it to burn off the coke, it works a treat and that little RXS is off like stink again. duno if its being mentioned before... but it works for my mates bike and that was a right horror to sort out. redex works a treat to compliment this
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A scientist crossed a skunk with an owl. He's got a bird that smells but doesn't give a hoot

[Arfdog]

Well, since putting the redex in, it's all been sweet. No more blockages (maybe the redex makes the carbon break into smaller bits which just get shot right out of the exhaust).

I can rev freely up to redline now, and I get 73 mph in top gear at the redline
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I'm a lover, not a fighter.

[gwernybwch]