Reed Valves

[tlanders]

In an earlier post, Thomas Carmicheal mentioned a reed valve kit from Boysen, but it has a Bultaco part number. Have any of you put reeds on a 250 or 400 Penton? And if so, what was the result?

Teddy

[dirtbike]

[?]
I'm curious too. You see I have this -81 KTM 250GS coming together at this point. I think that the motor is a bit pipey and not very good in lower RPM's. I have been thinking about trying to fit a -82 cylinder which still is air cooled and looks pretty much the same, but it has reeds.

If there is a considerable improvement, I will but I don't quite know what to expect. I have experienced pipey bikes with reeds and very smooth tractable engines without, like the OSSA Phantom and maicos.
Can anyone describe how a 250 -82 is running?

[Dr.2Stroke]

i had a 250 GS from 83 ,which had the same reed valve engine in it as the 82 250 MC had. The 82 250 GS was still without reeds,and had a piston steered cylinder on. The 82 250 GS is nearly the same edition like the 81 was.i rode such a 82 250 GS on the road this summer(beside a 600 ccm watercooled 2 STROKE....),and  in comparison of the two bikes,there isnt a big difference. the 83 has a little bit more power in lower ranges ,but it has the same "explosion " of power as the 82 has.so if you need more torque in the 250 81,build in a 420 ccm engine or a 495,thats like flying on a cruise missile.....

[tmc3c]

Hey Guy's if you have issue no.15 summer 2002 of Still.... Keeping Track, on page 10 TECH TIP'S " How to set up a winning Penton 250 motor, by Kent Knudson he has a lot of 'NEAT' idea's and I belive if not mistaken Al told me he is the builder of Kevin Brown's bike. Kent also goes on to write another issue of TECH TIP'S in the issue no.17 Winter 2002 I hope I have been of some help !

Thomas Carmichael

[tlanders]

I hope someone out there has done a reed conversion on the earlier engines. I would like to know how you did it and what the results were. Thanks,

Teddy

'71 steel tank Six Day (bought it new, ran Jack Pine and Bershire 2 Day International that year)
'73 Hare Scrambler (helped win AHRMA national motocross title 2002)
'74 Piner (won AHRMA national cross country 2001,2002)
'74 Piner (Alex's)
'74 Mint 400 (won AHRMA national motocross title 2002)
'75 Six Day (Sachs D)
'78 250 MC6/GS6 (I built it to do both, won AHRMA national cross country title 2003, second in motocross PV 50+ Intermediate)
'79 400 KTM (building it this winter I hope)
'01 200 EXC KTM (I have to buy a new Penton every 30 years)

[john durrill]

Teddy,
 I think the article was on the first gen engine. see if you have it at home . If not i can scan it and send it too you. Let me know soon, i go in for some neck surgery on thur morning and will be slow to respond for a week or so ok?
John D.

[john durrill]

dirtbike,
 you can install a lectron on the 81 and it will make a big difference in response at low RPM's . we have done that on both our 175,s and Speedy has several 7 speed hercules engines ( piston port). he has done that too for the same reason you are running in to( 175's and 250's).
 Al has some used Lectrons and you can get needles from Al or Speedy.
 the new Lectrons come with a power jet and can be  better for the later engines like yours though.
 Useing a Supper Trapp in place of the stock silencer will help also.
it will allow you to control back pressure some and change the reflected wave . that changes the rpm the pipe scavenges the cylinder. bounces the fresh charge back into the cylinder befor the piston closes the exhaust port off. you can adjust it with a wrench by adding or removeing disks while you ride.
 it has worked for us on both 175's the 7 fin and the later 77 and up 6 fin cylinders.
 you can do these things with the stock cylinder and be able to change the bike back to stock later easy.
 John & Peter

[tlanders]

John,

Are you referring to the Keeping Track article? I have it but don't remember Kent talking about reed valves. I'll check it out. Thanks, Teddy

'71 steel tank Six Day (bought it new, ran Jack Pine and Bershire 2 Day International that year)
'73 Hare Scrambler (helped win AHRMA national motocross title 2002)
'74 Piner (won AHRMA national cross country 2001,2002)
'74 Piner (Alex's)
'74 Mint 400 (won AHRMA national motocross title 2002)
'75 Six Day (Sachs D)
'78 250 MC6/GS6 (I built it to do both, won AHRMA national cross country title 2003, second in motocross PV 50+ Intermediate)
'79 400 KTM (building it this winter I hope)
'01 200 EXC KTM (I have to buy a new Penton every 30 years)

[Big Mac]

All I saw on the Kent Knudson set up for reeds was that they used the GEM 250/400 reed, which was a bolt on, ported piston as needed, and could get the replacement reeds from Boysen. Never heard much on the specifics of how it changed or improved power delivery. Didn't seem to be any cylinder machining required. Have found that GEM reeds for Penton/KTMs are exceedingly rare and never heard anything about other options, D&H or ?

Any other reed feedback?

[tlanders]

What got me thinking about this is I met a guy at the last AHRMA national in Alabama that has a mint 400 that he had reeds put on. They were not bolt on but had a box welded on the cylinder to hold a bigger set of reeds. He said there was extensive intake porting done to it also and that it was very powerful. Also I have been reading a book by A. Graham Bell entitled "Two Stroke Performance Tuning" last published in 1991. He goes through the developemnt of reed conversions siting that they were too small to begin with and they limited high speed performance, then by the early 1980s they were too big and now modern ones are somewhere in the middle. Does anybody know more about this kind of modification?

Teddy

'71 steel tank Six Day (bought it new, ran Jack Pine and Bershire 2 Day International that year)
'73 Hare Scrambler (helped win AHRMA national motocross title 2002)
'74 Piner (won AHRMA national cross country 2001,2002)
'74 Piner (Alex's)
'74 Mint 400 (won AHRMA national motocross title 2002)
'75 Six Day (Sachs D)
'78 250 MC6/GS6 (I built it to do both, won AHRMA national cross country title 2003, second in motocross PV 50+ Intermediate)
'79 400 KTM (building it this winter I hope)
'01 200 EXC KTM (I have to buy a new Penton every 30 years)