250 or 400cc...??

[iyaoyas]

Seller isn't sure which model variant he has so can anyone tell me what the piston dia. is for the 250 & 400cc KTM Engine?  Are there any distinguishing marks on the Engine to help identify the displacement? If so, where on the engine should I look for this info.?

Engine#: 54 30 003 010
Frame#: 54 411 79605

Thanks-

[Larry Perkins]

It is a 250 made late in 74 but is a 1975 model.

Larry P

[iyaoyas]

Thanks Larry.  He thinks the original 250cc engine was swapped out for the 400.  Here are a couple of photographs.  Your thoughts?

[Rocket]

If the engine number starts with 54 it is a 250.  A 400 would have serial number starting with 55.  The pipe looks like it is for a 400 motor.
RCG

[iyaoyas]

Thanks RCG...!  Owner says he checked the piston and confirmed it was a 400.  I'm not sure what he measured but it's unlikely that someone could have swapped out the cylinder, piston, carb. etc., due to the larger piston dia. and interference @ BDC with the crankcase...

[JP Morgen]

Whatever it is, looks like a decent bike. If the engine number starts with 54, it is a 250, no if, ands, or buts.

[454MRW]

It may be the casting #, which is posted, is probably on the engine case or clutch cover. The clutch cover and engine case is the same on both 250 & 400 engines. The number posted is not the engine serial #. To be sure, check the actual engine serial number, found directly below the cylinder fins on the right hand side, just slightly above the ignition cover. If it starts with a 54- it is a 250, but if it starts with a 55- number, then it is a 400. A STD bore 250 piston measures 71 or 72mm, a 400 measures 81 or 82mm. A pic of the area where the actual serial number is would be helpful. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1978-1979 MX-6 175 & 250 KTM's
1976-78 125-400 RM's & 79 PE250 Suzuki & 2012 DR650
2007 CR125R Honda
1977 MC250 Maico

[Larry Perkins]

Good eye Mike.  I saw the frame number and saw that what was supposed to be the engine number started with 54 and did not pay close attention to the rest of the numbers.  That is the part number of the sidecase.

Larry P

[iyaoyas]

Thanks Mike.  I've since asked for a photo of the engine number.  I'm not sure what a fair market value is for this bike.  According to the owner the engine will need to be rebuilt and from the looks of it, after having been in dry storage for several years, it will need just a 'little' bit of work to bring it back to life.  No worries though as this would be a fun project with the possibility for a full-on restoration down the road...

[iyaoyas]

I've confirmed the engine number is 4-5500857 so it's a 400 afterall.  Thanks to all who have contributed to this inquiry...!

[Dave Withrow]

Interesting quality upgrades on this one.....Works shocks and Lectron carb are the 2 I noticed.

[rob w]

The rear fender is on backwards

[iyaoyas]

Additional photo's...several of them!  So what's stock and what's not??

[skiracer]

Looking at the carb photo, there doesn't seem to be too much getting through that boot leading into the carb.......


1976 MC 5 Original Owner
1982 Suzuki PE 175
1976 Penton 175 XC
1985 20' Hi Point trailer