1984 KTM495 technical question

[KTM495]

I've been restoring a 1984 KTM495(see //www.ktm495.co.uk) for the last year. The engine is sorted and now the suspension is sorted. But now the suspension is letting me go quicker I need MORE POWER!!

The 84 runs a low compression (11:1) single plug head. The 83 ran a high compression (14:1) twin plug head and gave an extra 10 BHP. The 83 has got loads of low down torque, flat troque curve etc etc... But I want light switch delivery. It's funnier that way. According to all the 84 magazines I have swapping to an 83 head was the standard race tuning trick 17 years ago.

So... I have an 83 twin plug head on its way to me. The question is can I run with just the one plug? What problems am I likley to get?? or...

Can I run a second coil off the same motoplat?

or... do I have to buy the (very expensive) twin coil and correct motoplat setup to unleash the monster??

Any help much appreciated.

[email protected]



 

[Doug Wilford]

SI;
I am not an expert on the later Penton/KTM engines, I do know that you will have no problems using just one spark plug at a time with that head.  Put two plugs in and only use one.   Or plug the offset hole and just use one.   I will refer your question to our ex motoplat expert, now PVL ignitions at Penton Imports here in OHIO.


 

[John Lambert]

I owned an 84 495 MXC and it had a wonderful wide powerband.  The engine felt like a CZ 400 with a reed valve, but with more power down low.  I've also ridden and raced 81, 82 & 83 KTM 495's and I'll say the 81 was the most powerful, hardest hitting bike I've ever ridden.  If you want white knuckles, go for the 81 engine specs!!!

 

[KTM495]

Thanks Doug, John,

Quite a few people have said it'll be fine with one plug, including Mike (posts here sometimes) who's run with front, back and both plugs - all work OK. So I won't worry about messing with the ignition.

John - the 81 didn't have a reed valve did it? I think the 82-3 are the same and the 84 only differs in the head.

I've got the head now so I'll let everyone know if it makes it a bit more entertaining

 

[Larry Perkins]

I raced a 495 KTM in one of Casey Folk's World Championship Desert Races in I think 84.  the day before the race I was practicing bomb runs.  At about 100mph I wicked the throttle off quickly and it did a forever serious head shimmy/shake till I got the speed down to about 70.  It made me religious and my heart was probably never the same.  That was one serious fast scooter.  I am amazed that you seek more power.  What makes life interesting to us speed junkies is pushing the envelope.  Push on brother.

 

[KTM495]

Were you on the 84 though? The 84 was down 10 BHP on the 83.

Anyway... too much is never enough...

Talking of too much... I know a guy who's building a stroked (to 520cc) and ported 495... in a 125 twinshock frame.

[email protected]

 

[Roger Sibilsky]

You want light switch,arm stretching,suck your eyeballs to the back of your head power??Contact Rod Bush and have his guys give your cylinder and head some port work and combustion chamber massaging.He's your man for ridiculous KTM power!

 

[Mike Lenz]

They kept slowing it down almost every year since the 81. If you want insane power the 81 is the only way to go. Believe it or not I know of a guy that ports the 81's!!!!!! What the hell why your at it might as well put an internal flywheel ign on it too...And let us know where your racing it next. It would be worth a drive.

 

[Roger Sibilsky]

Can you imagine??Ultra light,balanced,welded crank,full on port and head work,Boswell reworked and massaged carb,Digital PVL internal rotor ignition,hand coned pipe and silencer and run it on alcohol??Where do I sign up??Let me ride!!

 

[gooey]

dont you think that at some point,,, a gun is cheaper  ok,, just kiddin !  (maybe kiddin ??)

 

[Roger Sibilsky]

Gooey...What are you gonna do with a gun??Shoot yourself in the foot so you wont be able to ride it??LOL :)Too much power is NEVER enough!!I know.After riding ported,polished,piped,carbed,foo foo Maicos for 20 + years,it's time to hop on the all mighty KATOOM!!

 

[KTM495]

Well Roger, Mike,

I can't see me sending the bits away for porting and I doubt if you'll want to come see it going 'cause I'm in England....

But I will be getting some video on the web.

And as for getting a gun instead... I kicked it over without a tailpipe in the garage just to see if it would fire. It did. Kinda like having a shotgun go off next to your head but sharper and louder. I'll wait until I get my tailpipe back from being welded before I run it

Si.

 

[Olmy]

Computer has not been working properly so I am a bit late getting into this conversation.  I have the 83' 495 with twin plug head and twin wire motoplat.  I run two NGK 9s and they both fire brightly when turned over in the dim light.  These plugs screw into the top of the head at angles.  They are not straight on top.  Through trial it seems to me that with both plugs firing the engine has quicker response.  It is hard to tell because of the crazy acceleration that one feels anyway.  I am ready to have my 495 rebuilt botoom and top.  I have all the parts just need the best place to take the engine to.  I live near Akron Ohio and have been thinking of Holeshot.  Any other suggestions??
Mike

 

[Olmy]

z

 

[Rocket]

I would imagine that the twin plug head and both firing together is because of the massive piston and higher compression ratio, to try and get away from detonation and have a better flame pattern in the combustion chamber.
Rocket
PS
I ride a 99 KTM 200EXC and I think that I have plenty of power.  You horsepower freaks are sick!!!!