Norton Motorcycle Tech Talk

Home

Printer-friendly copy
Online Resources
Norton Manuals / Dyno Dave / MotoCycles.com / Daytona Bike Week
Top Norton Motorcycle Tech Talk Forum Topic #1532   Previous topic | Next topic   
rusteezSun Dec-05-04 11:46 PM
Member since Mar 18th 2009
4 posts
Click to send private message to this authorClick to view this author's profileClick to add this author to your buddy list
"what is it? and what parts do i need"


  

          

i have had this particular norton heavy twin for 3 years now and just now have gotten around to the engine work, the engine #s on the bottom case is 107625, the head has the birco symbol underneath in a depression, the numbers i can make out are 06-0380 there are two small A's stamped underneath the head underneath each exhaust outlet, there is a C stamped on top of the head, there is also a small Ken stamped on the side of the head,lve not taken off the jugs yet because everything is in pretty good shape, it might need to be honed and ringed because of setting, but i would rather start new with pistons and rings so i now what i have in it, the size of the piston bore is a little short of 73mm. using a cheap digital mic, but is around 72.96mm, it had a copper head gasket, in good shape, on top of the jug, under the head, someone had marked in marker .040 TO or TC cant make it out, which stands for tolerence or ?, the cyl. are cas but i think the fins are alloy, there is a little piece of a fin missing on the very bottom of the jug and it is alloy. the motor is a pre- unit with a K2fc mag. the head is oil fed through the side of of rocker instead of on top like atlas, the bottom case breather outlet is gone and replacedwith a bolt and nut. if you can pleas help me so i can get this running finally, i can give piston #'s if it would help.

  

Alert Printer-friendly copy | Reply | Reply with quote | Top
dynodaveyMon Dec-06-04 07:03 AM

  
#1. "RE: what is it? and what parts do i need"
In response to Reply # 0


  

          

Sounds like a bitza
Possibly a 63 atlas bottom end (107xxx) and comando top end with a 750combat head(060380 head 72 with "C").

very similar....to one I'm building.
Not really something for a beginner to start on....but you got it, so run with it.

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

rusteezMon Dec-06-04 10:36 AM
Member since Mar 18th 2009
4 posts
Click to send private message to this authorClick to view this author's profileClick to add this author to your buddy list
#2. "RE: what is it? and what parts do i need"
In response to Reply # 1


  

          

thanx dynodavey, i just needed someone to help reaffirm what i had. i wasnt sure that it was a frankenstein but i am now, if you have any tips for me on the engine please give them, the rockers, timing chain, sprockets, gears, are all new, i just need to know what gasket set should i get? or do i have to buy two to make one? should i port and polish the head?, the head looks like new old stock. still need magneto work though, it doesnt run and missing parts. my rolling chassis is already completed, with ceriani road race front end. ive already spent alot of time and money, might as well go the distance. thanx again for your reply. i love the nortons.

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

dynodaveyMon Dec-06-04 11:29 AM

  
#3. "RE: what is it? and what parts do i need"
In response to Reply # 2


  

          

You can probably just use individual gaskets rather than a whole set. Are your bolts 5/16"atlas or 3/8 commando"?
You really need to find out what cam you have in it. You can compare to the cam specs in my tech articles.
The combat head IS ported out already and is considered by some to be already to big....especially if you're not building a road race engine and have a stock cam.

dynodavey(dynodave from work and can't log in)

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

rusteezMon Dec-06-04 10:38 PM
Member since Mar 18th 2009
4 posts
Click to send private message to this authorClick to view this author's profileClick to add this author to your buddy list
#4. "RE: what is it? and what parts do i need"
In response to Reply # 3


  

          

thanx again for your advice dave, youve became my new best friend, someone who knows what they are doing is always my best friend. anyway, before i pull the jugs, i thought i would ask about how i could tell if the motor has commando pistons, i have been reading your articles all night and have found them very valuable, how can i tell or could i tell what cam i am running without seperating the cases, it seems every part has #'s, and i am going to mic the pistons, just wondering what the clearance is for the rings? i need to gather all the info i can before ressurecting this beast. i also gather everyone on this web site is a firm believer in superblend main bearings. i have found more lettered marker telling that this engine was rebuilt in 96, just hope someone new what they were doing. again thanx for your feedback

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

rusteezTue Dec-07-04 01:54 AM
Member since Mar 18th 2009
4 posts
Click to send private message to this authorClick to view this author's profileClick to add this author to your buddy list
#5. "RE: what is it? and what parts do i need"
In response to Reply # 4


  

          

ok, here i go, i have taken the jug off, it seems like it might need to be honed or maybe go up a size in piston, there is some pitting and carbon build up, but no serious gauges or scratches, in cylinder or piston, just a little gauling on one piston, what would it do to the compression if i went up a size in piston running a .040 copper gasket and that combat head that is on it, tell me if there is something i should know, the funny thing is the pistons dont have any serious scratches but the bottom cases seem to have damage from the piston skirt. one of the piston rods is dinged up a little where it bolts to the crank, could this be from pre-ignition, timing? the cam lobes are good,too good, like new, is there a visiable difference between the combat cam and the commando cam without taking the cam out? As you can see, i am green around the ears when it comes to this motor, but i am learning, this is a lot different from hot rod 2 strokes. by the way the pistons are stock commando, i think, they measure out stock anyway, the bore doesnt seem to be wobbled out much. if this cylinder was honed, is there oversize rings available and would this be a good idea with high compression? thanx again for your time dyano dave.

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

dynodaveyTue Dec-07-04 08:48 AM

  
#7. "RE: what is it? and what parts do i need"
In response to Reply # 5


  

          

going up to .040 over on the pistons shouldn't do all that much to the CR,
However with a mag...you will want to pay very careful attention to the springs of the automatic advance unit to have a slow enough advance or it will ping and detonate.
Some of your piston damage may be from that???? When the springs get tired, it will even be hard to adjust the idle, since you could get idle runaway from over advancing from weak springs.
My bike is doing that and needs work too...

dd

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

dynodaveyTue Dec-07-04 08:39 AM

  
#6. "RE: what is it? and what parts do i need"
In response to Reply # 4


  

          

Commando pistons are flat top and atlas are dished.
IIRC both will be .050 above deck.

You could set the barrels back on the cases, and dial indicator off the top of the push rods for cam lift....add a degree wheel and get the full specs.

dd

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

Top Norton Motorcycle Tech Talk Forum Topic #1532 Previous topic | Next topic





Norton Commando Oil Change