Low mileage, semi-basket build thread

[Rohan]

Re: New Norton owner, 74 850, Help!

My Ducati F1 750 has angular contact main bearings. It wants .005" preload on the main bearings so I would say they expect .003"-.005" expansion of the cases when hot. If the rod journal isn't centered to the cylinder bore like when I got it and it was .03" to one side it shows up where the piston touches the head on one side after being revved to 11000 rpm. Once I shimmed it to center the piston touches more equal side to side and rings last longer. .

Angular contact bearings, and Ducati motors are a completely different kettle of fish ?
Commando engines have plain ole roller bearings each side, so the crank end float is not critical, in the slightest.
As long as the rollers stay on their tracks...
While centering the rods and pistons in the bores is good, there is a fair bit of leeway/float on the gudgeon pins in Commandos,
so 30 thou isn't probably even going to show up as a problem in a Commando engine, the piston can float to where it is needed ?(within reason)

However, cammy Norton engines, with their bevel drive gears to the ohc, need a slightly negative setup of endfloat when cold
- if the bevels pull out of mesh when they are at operating temp, they can destroy themselves - as more than a few owners have found.
And also may be noisy, into the bargain.
Assuming some engines are the same as other engines requirements isn't going to work...

Horses for courses ?

 

[Time Warp]

Re: New Norton owner, 74 850, Help!

Horses for courses ?

Which is why asked some months ago with no replies why Norton did not use angular contact mains like Ducati who combined them with shell big ends from around 1985,they stopped making real Ducati's shortly after but that is another story.
Perhaps it was due to not being able to fit them to Norton cases due to their diameter.
Bevel drive systems are not that hard to set up as long as you are methodical. (30 years experience)

 

[Rohan]

Re: New Norton owner, 74 850, Help!

Which is why asked some months ago with no replies why Norton did not use angular contact mains like Ducati

Probably have to ask the Norton Factory engine guys that one ?

Having a souce close to the factory that could supply them would be at least one factor.
And having solved the Combat problems with superblends, put the file back in the filing cabinet !

Got a number for the Duc bearings, and what sort of $$ they are ?

The Duc crankshaft is quite light compared to a Commando isn't it, (v-twin against parallel twin),
so the actual ability of the bearings to handle the weight is quite possibly a factor too.
Being able to handle a bit of flex and misalignment also, which the Duc probably doesn't do nearly as much ?

 

[Time Warp]

Re: New Norton owner, 74 850, Help!

Got a number for the Duc bearings, and what sort of $$ they are ?

RHP7307 both sides on 1971 to 1985 Beveldrives.
There is also a smaller roller bearing on the end of the crank r/h side at the bevels support plate and a ball bearing in the clutch cover that is the oil feed inlet and also supports the crank end.
My Brook Henry built engine has 2.2 kgs removed from the crankshaft webs and perhaps another 2 kgs+ off the outer flywheel.
Power to 8800 rpm and still flat at over 9000rpm.
I forget the stock weight but a different kettle of fish but in the grand scheme of things in that time period (British-American-Italian - Japanese ) somewhat interesting when brands were compared.
Ducati had their own troubles of course.

Item：7307X6 bearing
New Model No.：7307 B
Factory model No.：7307X6
Old Model No.：66307
Inner Diameter：35
Outer Diameter：80
Width：21
Brand：RHP
Type：Angular Contact Ball Bearings

 

[edgefinder]

Re: New Norton owner, 74 850, Help!

Angular contact bearings, and Ducati motors are a completely different kettle of fish ?

Assuming some engines are the same as other engines requirements isn't going to work...

I'm just pointing out that the Norton and Ducati crankcases are simular size and you could expect simular thermal expansion of .003"-.005".

If you go through the effort of shimming the crank better than it left the factory take why not go ahead and put the rod journals at the same centerline as the cylinders?

 

[X-file]

Re: New Norton owner, 74 850, Help!

Having the rods central will matter,as pointed out earlier.
Let's say your rods were off-centre in the cylinders by 0.030".Lets say the force on a piston is 6000 lbs at full throttle (it will be close to that).
How much bending moment does that apply to the small-end of the rod?Answer = 180 inch-lbs (15 ft-lbs).

I can live without that force on my rods and pistons,and all the extra stress and friction involved.Ignore it if you like,and think it will just go away.I'm happy if I can keep it within 0.004",even when the engine is hot.

 

[Rohan]

Re: New Norton owner, 74 850, Help!

Have a look at a Commando gudgeon pin and rod and piston.
The piston can float on the pin, a bit, so there will be no 'bending moment'.
This applies to most motors, for a good reason.... ?

P.S. A lot of v-twins have the rods offset in the pistons, quite a bit some of them, to allow for the common centre on the crankpin.
Doesn't seem to cause any problems - and we are talking half inch or more, not a few thou...

 

[fatmatt]

Re: New Norton owner, 74 850, Help!

Got the repaired case half back from my buddy today, looks great. Re-assembled the bottom end and I'm measuring 20 thou. end play. I plan to continue with the rebuild, checking for completeness and condition, order new bearings, the Old Britts shim kit, new fasteners and anything else that pops up, then tear down and reassemble w/ new gaskets and sealant. Is there a separate area of this forum that I should be starting a build thread in or just start a fresh thread here? Sorry for no pics today, I left my memory card at home. Thanks for the advice, everyone. I'm really stoked to finally be building my own motor and on an 850 Commando at that.

 

[Matt Spencer]

Re: New Norton owner, 74 850, Help!

Now Remember , THIS is what You Want to end Up With . its Spirit , anyway . . So take it easy ,

And We'll have NONE of this Rushing . :wink:

 

[DogT]

Re: New Norton owner, 74 850, Help!

I'd say just continue this thread, you can rename it if you like.

 

[fatmatt]

Re: New Norton owner, 74 850, Help!

Crankshaft showing 20 thou side play.

Is this right?

I didn't tap this the whole way on because I don't have a puller that I suspect is needed to remove it.

Is this the correct amount of links between timing marks?

Oil pump and chain tensioner in place.

I'm a little unclear about this step. What is the tool they mentioned? I'm not sure what a "contact breaker seal" is either.

The whole deal.

I need to order new crankshaft seals and a spacer kit but I'm having trouble navigating the Old Britts site. I guess I'll just give them a call. Any other good places to get parts?

 

[fatmatt]

Re: New Norton owner, 74 850, Help!

Now Remember , THIS is what You Want to end Up With . its Spirit , anyway . . So take it easy ,

And We'll have NONE of this Rushing . :wink:

That's the hard part. I'm dying to get this puppy together and thrash it through some turns but I really want to take the time to paint and polish everything and make her all shiny. I live near some of the best mountain roads in the country and although I have some sweet bikes none of them are quite what I'm looking for. My Yamaha SRX600 is amazing but a bit too small for my 6'1" frame to be comfortable for more that an hour or so of thrashing.

My CB400F is sweet and although it fits a bit better than the SRX, I miss the torque when I blow a turn and want to get back up to speed quickly.

I LOVE wrestling my CB750Fs through some super tight turns but still I could use some more torque. Can't wait to see how the Commando performs.

 

[rx7171]

Re: New Norton owner, 74 850, Help!

>>I'm not sure what a "contact breaker seal" is either.<<

This is the lipseal for where the camshaft end projects through through the timing cover into the space where the contact breaker assembly resides.
Item #18 034053 shown on Parts List Group 3 page.
The end of the camshaft is threaded and a special tapered tool is threaded into it so when the timing cover is installed the camshaft end can go through the lipseal without damaging it. This is a cheap tool that I believe is available from OldBritts. Once through the seal the tool is removed.

If you are having a problem navigating the OldBritts site to buy parts I suspect you haven't quite figured it out completely yet.
One of the reasons I use OldBritts so much is how much I like the ease of using their site.
They also give a 10% discount for repeat customers.

 

[Matt Spencer]

Re: New Norton owner, 74 850, Help!

couple of turns of sellotape , just on end of shaft , can do it . The idea is its a GUIDE for the timing cover Oil Seal ,
so it doesnt cut the lip , or tear it , fitting the Timing Cover on .

If the cams right , itll be on the overlap , near as damn , at TDC . - just before T D C .

 

[X-file]

Re: New Norton owner, 74 850, Help!

Have a look at a Commando gudgeon pin and rod and piston.
The piston can float on the pin, a bit, so there will be no 'bending moment'.
This applies to most motors, for a good reason.... ?

If the force on the centre of the piston is not in line with the centre of the rod,there will definitely be a bending moment.Most V-engines and opposed twins have the cylinders offset from each other to keep the rods centred on the piston.
Take this to the extreme.Put a rod in a vice and clamp the big end.Put the piston beside the small end of the rod,and slide the pin into the rod.Now you have the rod off-centre by about 2" instead of 0.030".Put a 6000 lb force on the centre of the piston and see what happens with a 1000 ft-lb bending moment.

Mini engines had cranked rods and you could see the uneven wear on the big-end bearings from the twisting it created.Put a piston into a cylinder and apply 15 ft-lbs to the gudgeon pin.See how easily it slides up and down the cylinder.

 

[Rohan]

Re: New Norton owner, 74 850, Help!

Tell that to the designers of those engines - it obviously doesn't make enough difference to matter ?

If the piston/rod has been designed to float on the gudgeon pin, a little, then Commandos were designed to cope with that ?
And even a quarter inch offset on a Commando rod is still applying force within the rod. ?
The force can't differentiate if it is on the centreline of the rod, after all.
It would be nice if it was centralized, of course, but not essential... ??

 

[DogT]

Re: New Norton owner, 74 850, Help!

Picture

A piece of tape will work fine on the end of the cam, just be careful with it and don't leave it inside the case. I think I used a piece of rubber tape.

OB is easier to navigate if you have the parts book which pretty much follows the groups. I think the old 68 workshop manual has some good info in it too, I don't think much changed other than the cam washers and the breather methods.

 

[fatmatt]

Re: New Norton owner, 74 850, Help!

Talked to Mike at Kibblewhite (KPM) today about getting the cases, cylinders and head media blasted. They said that they will not do the head w/o disassembling to prevent getting the media into the valvetrain. This makes sense to me. He offered to disassemble it for me and provide all the parts bagged and labeled. This, too, sounds like a great idea. I now have two conundrums. How difficult is head reassembly and even if I decide to tackle the head, while it is in such capable hands, what else should I have done? I took a CB750 head there a while back and got an estimate for about $3500 but that was for a full race set-up. I'm sure they'll make a similar pitch when i bring this in. What do y'all suggest is a reasonable amount of upgrade if any?

 

[Snorton74]

Re: New Norton owner, 74 850, Help!

If you're considering having someone to do the head, you should have Jim Comstock (Comnoz) do it. You can't find anybody better. FYI

 

[Torontonian]

Re: New Norton owner, 74 850, Help!

Money. Big. = D shaped ports etc. Australia. Small ports ,not big. Money pit. Ain't it grand ?