Heads up to you with foam airfilters on flatslides...

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HansJ
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Heads up to you with foam airfilters on flatslides...

Post by HansJ » Tue Sep 11, 2012 5:00 pm

Just wanted to give a heads-up, in case you have flat-slide carbs, a well-oiled foamfilter on the velocity-stacks and tight (no) clearance on the inlet valves, this is what can happen...


Image

Engine back-fired, lit up the filter, and whoops, there i was running around in the pit, screaming for a fire-extinguisher. Ignored by everyone, but luckily, the fire stopped by itself, without causing anything else to start burning. Wipe off, start up up, and another track-day had begun:)

Once i got home, i noticed all inlet valves had minus clearances. The engine was hard to start in the cold morning, and i guess the acceleratorpump squirted a surplus of fuel into the carbs, and then when it back-fired, all hell broke loose.

If i have the time to go to the garage, i will give another heads-up this week. That one concerns those with a YZF750 swinger, rear-sets and an "active ride-style". :D
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Killerwhale
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Re: Heads up to you with foam airfilters on flatslides...

Post by Killerwhale » Tue Sep 11, 2012 5:16 pm

Way ahead of you Hasse :)

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Re: Heads up to you with foam airfilters on flatslides...

Post by bagmaker » Tue Sep 11, 2012 11:06 pm

scary but not un-heard of.
Apparently the trick is to keep cranking and get it started, the fire then being dragged into the bits that should be alight on the inside.
I live in fear, the way mine backfires and carries on.
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Tarwetijger
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Re: Heads up to you with foam airfilters on flatslides...

Post by Tarwetijger » Wed Sep 12, 2012 7:46 pm

Hmm, I've never heard of this before. Thanks for the warning Hans, especially since I have the same setup (TDMR's trumpets, foamfilter) and a trackday coming up on friday! :shock: :roll:

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dandywarhol
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Re: Heads up to you with foam airfilters on flatslides...

Post by dandywarhol » Wed Sep 12, 2012 10:08 pm

As the man said - no inlet valve clearances are the problem - not the filters/carbs
1996 TRX 850, blue, Ohlins 46HRCLS, Race Tech Gold Valves, 0.90 springs, Venom pipes, R6 brakes............
1974 Yamaha RD250A, Candy Blue
1998 Yamaha SZR660, blue of course
1967 Yamaha TD1C 250, Blue and white

HansJ
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Re: Heads up to you with foam airfilters on flatslides...

Post by HansJ » Thu Sep 13, 2012 7:03 am

dandywarhol wrote:As the man said - no inlet valve clearances are the problem - not the filters/carbs
Correct. What puzzles me is that when i restored the engine, i put in new inlet valves. These should have been the 2nd generation, presumably sturdier and not resulting in tight clearances. Will have a look at them this winter.

In any case, a small fire extinguisher is high on my purchase list. There are many other cases in. A pit, where it could be handy...
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dandywarhol
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Re: Heads up to you with foam airfilters on flatslides...

Post by dandywarhol » Thu Sep 13, 2012 9:20 am

Hans - do you remember if the part number on the valves suffixed with -01? Maybe you were sold a batch of new original valves suffixed -00
1996 TRX 850, blue, Ohlins 46HRCLS, Race Tech Gold Valves, 0.90 springs, Venom pipes, R6 brakes............
1974 Yamaha RD250A, Candy Blue
1998 Yamaha SZR660, blue of course
1967 Yamaha TD1C 250, Blue and white

HansJ
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Re: Heads up to you with foam airfilters on flatslides...

Post by HansJ » Thu Sep 13, 2012 1:30 pm

dandywarhol wrote:Hans - do you remember if the part number on the valves suffixed with -01? Maybe you were sold a batch of new original valves suffixed -00
I believe i ordered those, that's why i refer to "2nd generation". But i'll have to double-check that.
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