Dunstall 850 overhaul

Joined
Nov 1, 2014
Messages
908
Country flag
so i finally bought an emgo steel tank to replace the fiberglas, and here we are painting. so back in the day before it was dunstallized, it looked like this,

74norton-JPN.jpg


now.

20210417-163920.jpg

20210417-163937.jpg
 
Joined
Nov 1, 2014
Messages
908
Country flag
tank is done picture to follow, now its time to rid the world of a set of amal fuel meters, the right side is plugged up again, and i can't seem to get the tiny needle in to clear it. Jim Schmidt special PWK's
P1020710.jpg



new throttle cables installed, and waiting for a set of pod filters, it now starts on first kick, although trying to adjust the idle air mix is a real bitch because the ign switch bracket is blocking access to the screw on the left side...
 

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
16,458
Country flag
It’ll be interesting to see how you get on with the new carbs.

And even more interesting to see pics of the newly painted tank.

Come on now... stop teasing...
 

grandpaul

VIP MEMBER
Joined
Jan 15, 2008
Messages
12,146
Country flag
And even more interesting to see pics of the newly painted tank.
Yep, always interesting to know if a particular tank (depending on manufacturer), on a particular bike (depending on it's suspension and tire setup), with that particular paint scheme, will have it's horizontal paint lines level with the road when the bike is standing flat, upright...
 
Joined
Nov 1, 2014
Messages
908
Country flag
Yep, always interesting to know if a particular tank (depending on manufacturer), on a particular bike (depending on it's suspension and tire setup), with that particular paint scheme, will have it's horizontal paint lines level with the road when the bike is standing flat, upright...
we should be close, i set the tank in place to line up the strips, so the angle is ok, but they could have ended a bit lower, the tank is one of the Emgo pressedunits, and they are quite heavy, way heavier than the dunstall fiberglas unit.,i need to ride it tomorrow, and i still don't have a back strap for the tank, so i will not get you a picture with it mounted til a bit later.

as for the pwk, i just need to get a manometer set up to balance them and set the idle air circuit and we should be fine,
P1020712.jpg

the masking tape tried to peel the white paint after the stripping , but considering i didn't spent $1000.00 im happy with the end result, gotta give a big thanks to htown16 for helping with sourcing the paint colours, self etching priimer, high build primer, 3 coats white, sanded 1000, 1500, 2500 grit, then the strips and spray 2k max as a clear coat
 
Last edited:

grandpaul

VIP MEMBER
Joined
Jan 15, 2008
Messages
12,146
Country flag
The masking tape tried to peel the white paint after the stripping , but considering i didn't spent $1000.00 im happy with the end result, gotta give a big thanks to htown16 for helping with sourcing the paint colours, self etching priimer, high build primer, 3 coats white, sanded 1000, 1500, 2500 grit, then the strips and spray 2k max as a clear coat
Way better than anything I've ever done!
 
Joined
Nov 1, 2014
Messages
908
Country flag
the long weekend in August is the vintage motorcycle rally in Biggar SK. last yrs event was cancelled but this one got the green light so I decide to run the norton out for the festivities, I discovered that the ethanol was munching its way through the dunstall tank. bad news worse, it ate 1/2 a litre of engine oil to make the 220mi trip, shoulda cracked the engine open before i set it in the frame, now its a lot more work, and that bastard rear nut... anyway it seemed to me that there was a lot of oil in the cylinders...

20210803-160532.jpg


20210803-160621.jpg


the right plug was black and sooty, the left was black witha brown tones around the centre electrode. I don't believe this engine has been open since 1978 when the cam was replaced. you can see cross hatching in the walls an so very slight scratches vertically but cant detect them with your finger.

first i will pull the valves, and then we'll talk some more
 
Joined
Jan 5, 2019
Messages
2,254
Country flag
I couldn't complain about what I see of your cylinders. Those look practically newly done.... I stick the camera down the plug holes on mine periodically and you surely wouldn't like what I've got if you're upset over those.... I have oil, carbon, pots & pans, beer cans and all manner of blackest sin inside, but burn very little oil and no problems. Anyway I hope you get it fixed up so you can ride whilst good weather holds.
 
Joined
Nov 1, 2014
Messages
908
Country flag
i suppose the oil ran in from the head drain line, compression check was 120psi for both cyl cold.
 
Joined
Nov 1, 2014
Messages
908
Country flag
okay so back to basics, i pulled the rockershafts and 3 were pointing the wrong way. I am offended that someone would call what pulled out a valve guide seal. there is some wear in the valve guides, the manual says x and y direction should be the same , and they are, the wear is even, slight but detectable, i will measure.

i need to find someone to hydro/vapour blast this head, so the i can test the areas around the valve guides for leaks.

back in 1978 i had the dealer put in a new cam, i had no tools or space to do it. and then after the fix i sold it, it went through 4 owners before it came back home, so i am missing all maintenance history from 1978 to 2017. i would have hoped that the dealers mechanics knew the correct procedure to install a rock shaft.


any thoughts? would just having the rocker shafts pointing the wrong way be enough to cause the engine to eat and dump oil?
 
Joined
Nov 1, 2014
Messages
908
Country flag
I touched base with Jim Comstock, he's still really busy and has had some health issues too, We had a horrid time with UPS getting the parts to him last time. I wont ship it with the post due to all the covid delays, so wound up going to a local shop. They verify my measurement on the valve guides, which need to be replaced. They ordered a set of kibblewhite (KW) guides. i ordered a set of KW valve springs and seals. i really wanted to do the conical springs but among all the other expenses right i just could do it.

So it looks like someone was into the head before and replace the valves and seals, because the valves sized up new. but they used the crappy factory black neoprene seals.

so while the bike is waiting for the headwork to progress, i've been concocting a repair for the sagging side stand. On mine the hardened bushing has worn out the soft side stand head. I am going to weld on a piece of angle steel on top of the side stand and the run the bolt up through it . in this way the tight fit will significantly reduce the wobble, and i should get a few more miles out of the side stand before it needs to be replaced entirely. will post a picture when we have the pieces cut.
 
Joined
Nov 1, 2014
Messages
908
Country flag
P1020720.jpg


P1020721.jpg


It now folds up nice, but i see that with worn parts, the bolt is rotating too. a proper redesign, would put a bushing all the way through...
 

gortnipper

VIP MEMBER
Joined
Nov 11, 2013
Messages
4,867
Country flag
IIRC the pivot spacer sits just slightly proud of the side stand and the mounting lug so the bolt binds it and does not rotate.


IMG_20210919_120943.jpg
 
Top