The allen bolt mentioned above.......

[Steve Minor]

I forgot to mention the allen bolt mentioned above is rather large.....seems wrench required for removal was at least 10mm.

 

[Larry Perkins]

Steve,

Is this on the front side of the cylinder?  I think I remember a place on the back side of my 400 cylinder that is for a compression release.  We are probably talking about the same thing.  Hope this helps.

 

[Steve Minor]

I could have sworn it was on the exhaust side but now that I think, it could have been on the carb side of the cylinder....either way, it's the only horizontal projestion in the "jug"....It might very well be a location for a compression release......

 

[Larry Perkins]

Yes, I went and looked.  There was a Magura compression release available with a Magura lever that worked there.  I have a couple of those kits somewhere in the Misc. stuff.

 

[Steve Minor]

Larry......Thanks.....again...I wondered what it was and felt sure someone more knowledgable than I would have the answer...Ever found much use in, or need for, a compression release? I'm putting together a 1977 400....should I consider installing one?

 

[grandpaul]

A port for a compression release on the "jug" (cylinder) I though the compression release port was on the head, like a spare spark plug hole....


GrandPaul,
Host of the Vintage Bikes forum at //www.delphi.com/oldbikes and the Triumph Bonnevilles Forum at //www.delphi.com/grandpaul

[Steve Minor]

Ya know, I've only seen compression releases in the head too...But what explains the horizontal port in the side of my 400 cylinder then?....It's allen headed and short...almost like some sort of plug...I believe a 10mm allen wrench fits it...I remember it to be on the carb side of the cylinder....What are your thoughts?.....

 

[SCOTT CURTIS]

I have a 73 400 Maico.  The compression release is located just above the Carb in the cylinder not the head.  Works great for starting the big bore!!

 

[Steve Minor]

Scott...I'm showing my ignorance again....I'm not sure I understand how a compression release can make a big bore easier to start....would you explain it? I know it take a mule kick to start my 400 (when it's not broken that is)....should I consider installing one?

 

[Larry Perkins]

Ever now and again with a big-bore you will kick and catch it just coming to Top Dead Center and it will fire and kick you back very hard.  I had a Mint 400 in 1975 that was bad at this.  Maybe there was a timing thing going on too because I used to mess with timing a bunch to tune the engine for a purpose on bikes.  Anyway the compression release makes easy to get the piston just past TDC so that your kick catches it initially going down so as to avoid the whack.  Of course it carries a dual purpose as it is real fun to come up behind someone riding and pull in the release-WAAAAAAA.  Not as fun as a good waterhole whoosh on someone but close.

Seriously, the release is handy on the Penton but not a necessity in my opinion.  Now my WR400F Yamaha fourstroke is another story.  Decompression is a must.

 

[Chris Brown]

The new cylinder I put on my 400 had the port for a comression release. Was able to get one to plug the hole, but never hooked up a cable to use it. Don't find starting particularly difficult other than lots of compression. You really have to jump on it.
One thing I did find useful for cold starts  though, that is to tickle the old Bing to overflow, then pump the forks a few times to "spill" some fuel into the intake. Starts with a couple of good kicks. First kick with some throttle, then without. They are quite lean on start without a choke circuit.
I would have been happy with a plug for the CR release.
Chris

 

[Steve Minor]

Thanks for the input Chris....I have a choke/cable control on my Bing (guess 'cause it's a GS6 model)so starting was never too hard (when it was new that is)....You just had to jump off of ladder onto the kick start lever...serioulsy, it did take quite a mule kick...

 

[SCOTT CURTIS]

Steve, I actually kick start the bike holding the compression release open making it much easier to kick.  I quickly close the release once the bike is running.

 

[john durrill]

Steve,
Did you get the cylinder separated from the piston?
John

 

[sachsmx]

Its a good idea to use a compression release on these older big bores with expen$ive kick start mechanisms and levers, IMO. It's not only easier on the riders knees and legs to start the bike, but also easier on the gears, shafts, etc.