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Discussion in 'Trials' started by motobene, May 23, 2017.
Here is the part, assembled.
Sorry to clutter the thread with ramblings from a simpleton, but aside from the lack of beautiful machining, what are the disadvantages to the setup I have? Is it too restrictive?
My bike was occasionally doing some weird stuff at idle at Sipapu, it felt like it wanted to stall. That being said I have no idea what jets are in it, and I've only had it 3 days at this point. Power felt fine everywhere other than going up some of the ski runs but I attributed that to a gappy transmission more than jetting. I'm curious to hear your thoughts.
Lean on the pilot and rich on the main. Read Bene's jetting suggestions.
Also, as you go up in altitude, idle will drop. Sipapu has a rare significant altitude change within a single event.
I failed to run an over-high idle at the bottom of the hill and got myself two stall fives on sections at the top of the hill Sunday (plus my 250s carb is acting inconsistently).
Thanks for the pointers. Carry on.
The spark arrestor setups on the two 2017s worked flawlessly at the Sipapu events.
I just bought a 2017 Gas Gas 250 and I'm baffled (ha!) by how difficult it is to get a spark arrestor on it and be legal. Can someone suggest how I can go about doing it?
I ordered an exhaust adapter and Spanish Fly screen arrestor, but only received the latter. I don't think the supplier is going to come through soon with the adapter.
Wanna take bets on how long before this falls off?
The set screw is just kissing the end of the pipe, so I used a bunch of high-temp sealant to fix it in place, with a safety wire tether.
28 minutes, what do I win?
Ha! It stayed on for nearly two hours!
I had to pull it off when my bike stalled and wouldn't restart. I thought it was clogged.
a 2 stroke with an exhaust system that is quite long like every 2 cycle motorcycle ever made cannot produce a red hot spark out the tailpipe anyway
the whole shitty deal is based on an old chainsaw with an extremely short path from exhaust port
The silicone solution will last as long as Mr. Fly doesn't get whacked from a side or end fall, which could be the life of the bike under a more skilled rider that crashes infrequently. RTV silicone cred is good for about 600 degrees F.
If it does get knocked off you can just adhere it on again. With a tether it's no worries, mate!
Not true. I let a friend ride my 2003 GG280 Pro on a short trail ride, I followed behind on my wife's CRF230, we had done maybe 3 or 4 miles and were back on the road headed home when I got close I could see the red hot sparks coming out of the tail pipe. After being ridden at 1/2 to full throttle for 15 minutes or so the exhaust got hot enough that the carbon build up on the spark arrester screen was flaking off and producing the glowing sparks. The bike was very hot, but not "boiling over" hot. I will say that the bike was jetted way rich, had just moved from NJ (sea level) to NM(7000' +). And trials bikes get very hot when ridden at a trail bike pace. Probably an unlikely scenario for most, but possible. Also I learned how important it is, not just to have a spark arrester, but to clean it regularly.
Yes, the s/a screen caused the carbon build up and the restricted flow contributed to the overheating. Just like catylitic converters causings fires in tall dry grass.
Just a heads up for those of us that need to run these things.
You need to clean them out on a very regular basis!
I check it after every ride and have found "stuff" stuck to the inside many times.
It is a filter and there is significant flow going through it. My bike was fit with it from new and I recently found some translucent flakes 5mm in diameter stuck in the trap blocking flow. I assume sluff-off from the new exhaust.
I was glad to slip both of mine off after my return from New Mexico. We don't need/use them in Oklahoma, and the bikes run just a tiny bit better without them.
My way of cleaning them when I do use them is simple. I pressure wash the screen with it on the muffler as part of cleaning the bike. I start the bike after washing so whatever water gets into the muffler is blown out.
Muffler hydrophobia and anality of "muffler plugs" used in the fast off-road community give me a good chuckle.
Brand new bike or fresh repack on a silencer, run the bike without the screen sparky for a bit. This will allow the loose fiberglass packing to come out and not plug the screen. I've had it happen to me on a repack.
Randy Hawkins lost a National Enduro Championship in 2002 due to this. Sparkys were required at New England National Enduro, so his mechanic took his YZ250 2T silencer apart, repacked it and installed a 4T screen in it. Bike ran like crap all day. They swapped carb, ignition, fuel and finally too late stuck a screwdriver through the screen in the silencer.... Bingo ran fine!
Good to know.
This one came on my 14 Sherco, I really like it, weighs nothing, easy off and clean.
Was the pipe tip extended? The pipe tip on my '14 is flush with the muffler body end cap. I wouldn't be able to mount a spark arrestor on my Sherco (like that).