400 Enduro head Mod. to 45 cc ???

[Timothy Walls]

So in reading a Aug.1975 "Keeping Track ". JP says to make the 400 run better for enduro's the head should be machined or cut to 45cc. So what does that mean and how do you tell if it's been done or not ? It also say's to just send it back to Penton Imports and they will machine it for FREE .

Timothy Walls

[Daniel P. McEntee]

Hi Tim;
  The 400 has a real wild and woolly engine in it! Some (like me!) can find them hard to even kick over and with a light switch like power band. Increasing the combustion chamber volume to the 45cc is like cutting a new dome in the head. It takes the edge off the compression a bit and evens out the combustion cycle for smoother power. There has bee a fair amount written about it here on the forum and a search should turn it up. Dane Lienbech made a lathe tool with the correct curve on it for cutting the heads back in the day, and it is supposed to still be in existence today. Some one at Penton Imports had it and quoted me on doing my head, but I sold the bike before having it done. Chicago Jerry can do it and maybe at least one other maybe that I can't think of right now. You might check with Gary Ellis also.
  Type at you later,
   Dan McEnte

[Normandy10]

Chicago Jerry Gakauskas did mine for me, shipped it to him, had it back in about 5 days. You can find him on the forum here. He has the original plans from Carl Cranke.

Mike

[Mike Lenz]

They made two thicknesses of head gaskets also.  Maybe the thicker one for woods riding?

[john durrill]

Tim ,
I had a 79 400 GS . if you could find that head and cylinder you will be amazed what a great enduro/trail bike the 400 could be. I was a small bore rider most of my riding life , 100 ,125 ,175 .That was the last production of the first gen 400's. It was easy to start pulled like a huge electric motor , very stable and controllable it tight woods and mort speed than most folks can handle when the trails  opened up . Paul  or Ron would be folks to ask if it is possible to do the change out. I have a good picture of it after we restored it  but I no longer have a way to upload the pic online. It was fast enough we fitted a disk brake on the front because we ran a lot of water and mud where we live .
Just a thought chuckle chuckle !!
John D

[Larry Perkins]

The head mod makes it as easy to start as a 250.  Great improvement!

Larry P