'79 KX250A5 with '79 KDX400 engine fitted ... KX400A5

[Speed]

Great, and I'm betting it will help with engine heat as well.   If the outlet is too restrictive, the pressure in the pipe will be higher on average than it should be.  Leading to higher gas temperature in the pipe and the pipe will be resonant at a higher rpm and if it is excessively restrictive the exhaust gases will not be able to evacuate the cylinder completely by the time the transfers open and you will get hot gases traveling down the transfer feeder/ducts, mixing with and heating that mixture in the transfer ports and everything else along with it, piston cylinder and crankcase. 

I have seen this more than a few times 83 KX500's was one bike that this was a problem.
And I've just recently seen it in a big bore Yamaha.  In the Yamaha there was even carbon built up in the transfer ports.
This thing knocked it's head off.  All good now..

Bla Bla Bla.  I got on a roll then.lol..  Anyway I'd love to hear how your engine heat problem is now.

[Lozza]

That's why 500's and most enduro's  have very long mufflers, 125 short and why Eric Gorr and a host of other engine tuners other engine tuners recommended cutting mufflers on certain bikes , 93 RM 250 for eg, to get them to rev on a bit more. On and on and on....

....

talking about stingers not mufflers ...............

[Lozza]

Great, and I'm betting it will help with engine heat as well.   If the outlet is too restrictive, the pressure in the pipe will be higher on average than it should be.  Leading to higher gas temperature in the pipe and the pipe will be resonant at a higher rpm and if it is excessively restrictive the exhaust gases will not be able to evacuate the cylinder completely by the time the transfers open and you will get hot gases traveling down the transfer feeder/ducts, mixing with and heating that mixture in the transfer ports and everything else along with it, piston cylinder and crankcase. 

I have seen this more than a few times 83 KX500's was one bike that this was a problem.
And I've just recently seen it in a big bore Yamaha.  In the Yamaha there was even carbon built up in the transfer ports.
This thing knocked it's head off.  All good now..

Bla Bla Bla.  I got on a roll then.lol..  Anyway I'd love to hear how your engine heat problem is now.

A too small stinger will send an engine into pre-ignition in a very short time seconds even . Black soot in the transfers is a sign of insuffiecient blowdown angle/time area not a too small stinger. Most of the hottest exhaust gas leaves the cylinder just as the exhaust port opens(highest temp and pressure).             

[oldyzman]

Hi John. I know you said it is only a club level bike but it can still be protested. The steward will just refer to the MoMS for clarification. The top triple clamp could also be protested with its vertical risers.Different meet. Different steward. Shit happens.
I don't give a toss. The bike looks great.

These sort of rules just shit me. A not so rich dirt tracker who cannot afford to shorten the forks can just push them through say an inch to lower the bike. If the handle bars are in the way then use a riser or fit fat bars /converter which also rises the bars to allow the forks push through. IMO There is no possible performance gained when fitting handle bar risers.

[Speed]

Great, and I'm betting it will help with engine heat as well.   If the outlet is too restrictive, the pressure in the pipe will be higher on average than it should be.  Leading to higher gas temperature in the pipe and the pipe will be resonant at a higher rpm and if it is excessively restrictive the exhaust gases will not be able to evacuate the cylinder completely by the time the transfers open and you will get hot gases traveling down the transfer feeder/ducts, mixing with and heating that mixture in the transfer ports and everything else along with it, piston cylinder and crankcase. 

I have seen this more than a few times 83 KX500's was one bike that this was a problem.
And I've just recently seen it in a big bore Yamaha.  In the Yamaha there was even carbon built up in the transfer ports.
This thing knocked it's head off.  All good now..

Bla Bla Bla.  I got on a roll then.lol..  Anyway I'd love to hear how your engine heat problem is now.

A too small stinger will send an engine into pre-ignition in a very short time seconds even . Black soot in the transfers is a sign of insuffiecient blowdown angle/time area not a too small stinger. Most of the hottest exhaust gas leaves the cylinder just as the exhaust port opens(highest temp and pressure).           

Yep, agree.  "  A too small stinger will send an engine into pre-ignition in a very short time seconds even".
But do you disagree.   That If the stinger and or muffler is excessively restrictive the exhaust gases will not be able to evacuate the cylinder completely by the time the transfers open and you will get hot gases traveling down the transfer feeder/ducts, mixing with and heating that mixture in the transfer ports and everything else along with it, piston cylinder and crankcase?

[oldyzman]

Does this also mean too big of a diameter muffler ie 38mm id on say a 250 2 stroke could also cause detonation?
Brett

[Ted]

Hi John. I know you said it is only a club level bike but it can still be protested. The steward will just refer to the MoMS for clarification. The top triple clamp could also be protested with its vertical risers.Different meet. Different steward. Shit happens.
I don't give a toss. The bike looks great.

These sort of rules just shit me. A not so rich dirt tracker who cannot afford to shorten the forks can just push them through say an inch to lower the bike. If the handle bars are in the way then use a riser or fit fat bars /converter which also rises the bars to allow the forks push through. IMO There is no possible performance gained when fitting handle bar risers.

The protest wouldn't come from raising the bars but from moving the bars further forward ( like a modern ) which these clamps enable you to do. Yes it is an enhancement. Yes they are off a model that we thought didn't comply with Evo. However if Dave Tanner gets his interpretation over the line they will be ok for Evo, along with a 84 KX 500 in it as well.

[John Orchard]

Does this also mean too big of a diameter muffler ie 38mm id on say a 250 2 stroke could also cause detonation?
Brett

My guess is that it won't be causing detonation but you could be losing some top-end power.

[FourstrokeForever]

Hi John. I know you said it is only a club level bike but it can still be protested. The steward will just refer to the MoMS for clarification. The top triple clamp could also be protested with its vertical risers.Different meet. Different steward. Shit happens.
I don't give a toss. The bike looks great.

These sort of rules just shit me. A not so rich dirt tracker who cannot afford to shorten the forks can just push them through say an inch to lower the bike. If the handle bars are in the way then use a riser or fit fat bars /converter which also rises the bars to allow the forks push through. IMO There is no possible performance gained when fitting handle bar risers.

The protest wouldn't come from raising the bars but from moving the bars further forward ( like a modern ) which these clamps enable you to do. Yes it is an enhancement. Yes they are off a model that we thought didn't comply with Evo. However if Dave Tanner gets his interpretation over the line they will be ok for Evo, along with a 84 KX 500 in it as well.

How the hell does this get into a discussion about exhausts on a bike where the owner/builder doesn't give a toss about NATIONAL eligibility? He just wants to ride a very nice bike that he built with his own 2 hands....unlike some people who get others to build their bikes and then stick some young bloke on it at a national event to do what they can't..... If eligibility is what you want to discuss, use the administration of competition thread. 

[Ted]

I'm talking to the bloke that sold me said bike. Pull your head in.

[FourstrokeForever]

I'm talking to the bloke that sold me said bike. Pull your head in.

Head is pulled in......

[John Orchard]

A business proposition has arisen, looking at moving-on the big KX/KDX, specs as follows ......

KX250A5 ('79) chassis.
KDX400A1 ('79) engine, mildly ported, head squish set.
KX500 ('83) gearbox.
KX125 ('83) front-end.
TT600 ('83) triple-clamps (rubber bar mounts).
Near new YSS shocks.
Fresh resleeve, new standard KDX400 piston & rings, sleeve with enough meat to fit KX420 piston.
Carbon reeds.
New wheel bearings front & rear.
New headstem bearings.
New swwingarm bearings, bushes & seals.
New brake shoes.
KX500 all-plastic chain-guide.
Wide stainless footpegs.
New Unifilter airfilter.
Fresh engine bearings & seals.
Heavy duty clutch springs.
New clutch plates.
New custom-made seat cover - KX250A5 with KDX screen-print.

SPARES
----------
KX250A5 front wheel.
KX250A5 forks, disassembled, one leg slightly bent.
KX250A5 triple clamps x 2.
KDX400 rear hub, painted with new bearings ready for lacing to a rim.
KDX400 gearbox.
KDX400 mag cover.
KX420 gearbox.
New fuel tank & sidecover decals.
New & used front & rear sprockets.
Reed cage.
Clutch plates.
KX250A5 seat cover (used).
New KDX175 'period' Maier headlight shroud.
New TY tail-light.
New KDX400 gasket kit.

Plus heaps more KX & KDX bits & bobs that I will not need anymore.

The bike is great to ride, the only thing I think it needs to complete it is a GMC pipe, the modified KDX400 pipe works ok but looks a little untidy.

$4500 can get you a VERY rare & admired bike, it breaks my heart to sell it, but of all the bikes I have for sale, this is probably the most sort-after.

[FourstrokeForever]

Leg End Ted told us all that he bought the bike 

[John Orchard]

Leg End Ted told us all that he bought the bike 

Ted bought an RM125B off me a couple of years ago (the one with the alloy swingarm ;-) )

Getting to turn-1 first at Viper a couple of months ago....

[John Orchard]

Still avail for sale, selling due to the onset of my old-age.