The new guy on the board..

[Ventodue]

Hi John,

Welcome from another 450 SCR owner!



Just one thing to add to the advice you've already been given: there really is no point in repeatedly kicking a Ducrappi single! If it doesn't go after half a dozen attempts, find the problem.

You've got good compression, so the valve timing is there or near enuf. And the fact that it will start and run means you've got a spark and fuel. However, it's possible that the carb still needs a proper clean to give easy starting - ultrasonic is THE best way, btw.

Jets should be (with air filter fitted): idle, 45; mains, 130; atomiser, 265T (without filter: 50; 135; 265T). Needle: V7, on the middle groove. Initial settings for the screws: mixture screw, 1½ turns out; slide screw, 2 turns out and then back out to slow tick-over if necessary.

Ciao e buona fortuna!

Craig

P.s What plug are you running, btw? Should be a NKG B6HS. 0.8mm gap.

[DewCatTea-Bob]

By: john jupiter...
" i actually love the name, it sounds like a 50's du-wop singer and its really growing on me "

____ Well I suppose so, but I'm more so reminded of George Jetson (of 'The Jetsons').


" took your advice and made my own cables today, it wasnt very hard "

____ It would be nice if you'd tell how you went-about it, so others might copy your positive experience.


" I do have a title, but not the original. Dont you need to turn the titles in as the bike changes hands? How would one keep the original? "

____ Well at least in some states the (signed-over) title can remain in your hands until you turn it in to be re-registered into your own name, and even at this considerably later time, it can still be possible to find an original-owner of a Duke.
__ Anyway, what info is still included on the title you have? ... Got the model-year?


DUKE-Cheers,
-Bob

[MotoMike]

JJ

that is good looking Jupiter. Looks pretty complete. I do wonder what I'm looking at when I scrutinize the swing arm pivot. Is that a big bolt and nut going through there? My 450 has that same tail light I think and I've come close to loosing it a couple times. Some thread locker is a good investment!

These carbs are pretty simple. I've in the past on different motorcycles had odd starting running problems that I attributed to the carb. It doesn't take much to make them act up. I've taken them apart, cleaned them and not really seen anything wrong but when reassembled and reinstalled the problem had gone away. In most cases I've been able to do a good cleaing with a can of carb cleaner and an air hose. I would think the best carb cleaner is the kind you buy in a gallon can with a basket in it that allows you to put the parts in a bath. that stuff works like a champ, but if you are like me with seldom needing it, it might be over kill. Never used and ultrasonic cleaner for carbs.

Mine did not have the compression relief when I got it and I've since decided I don't need it. I rotate the engine up against compression then (key off) apply slow steady pressure on the kick starter as the compression bleeds off till I just get over the top, then key on, choke, (tickle in my case) and kick to start. If I remember right the manual tells you to give it an 1/8 turn on the trottle. Good luck.

[DewCatTea-Bob]

" My 450 has that same tail light I think and I've come close to loosing it a couple times. Some thread locker is a good investment! "

____ The attachment-nut's coming loose & lost is just a clue warning of an even greater concern ! ...
Those stock brackets are doomed to becoming all cracked-up in multiple spots if something isn't done to help prevent that certainly eventual happenstance !
I-myself use rubber-washers between fender-washers where-ever possible ! _ AND avoid cold-weather riding !
Otherwise, don't expect much more than 2000-miles of good life, (3k-miles of useable-life), out of those (flimsy!) brackets, on a 450.


Hopeful-Cheers,
-Bob

[john jupiter]

Motomike: thanks for the info! that swingarm bolt is suspect... i attached a close-up of the rigged up bolt and washers. what is it supposed to look like?

Dew cat tea Bob: its titled as a 1970, the engine numbers confirm this when compared to the sheet of known engine numbers put together by Paul Miller, although the frame tag on the steering neck is not currently present. previous owner says he has it somewhere and is in the process of finding it as he cleans out his garage.

[MotoMike]

Hi John

I think that the swing arm pivot is inserted in place and held there by the pinch bolts at the end of the mounting tube. Others have more experience than me and can probably add to this.

You mentioned problems with cool iris. I have a real slug computer that I look at it on and don't have a problem. I thought initially it was not working because I didn't select the page I wanted to look at and thought the resolution was too poor to do anything. but once the operator error was cleared, I found it to be pretty slick. If the Cool Iris won't play though, I think in the tech section there are a few pdf format books that will help you.

Regards,
Mike

[DewCatTea-Bob]

" I think that the swing arm pivot is inserted in place and held there by the pinch bolts at the end of the mounting tube. "

____ With mostly SCR.models, the pinch-space gets filled with dirt and then the pinch-bolts can't be tightened-down easily enough to keep the pivot-spindle from getting vibrated out of normal/centered-position. _ So possibly a previous-owner over-tightened & stripped the threads for the two pinch-bolts, and so came-up with the large/long bolt & washers to more securely keep the (hollow) spindle-shaft held centered, in normal position.
__ It's a fairly common issue that if the pair of stock pinch-bolts are not keep tightly snugged, the pivot-spindle then gets worked-outward and thus one of it's plastic-covers is then lost,, especially with the shaky 450, or even the smaller motors with loosened motor-mount bolts -(contributing to increased vibration).
__ On some Dukes used only for dirt-riding, I've employed a similar mod but, (instead of such a large bolt), rather with the use of a length of 1/4" threaded-rod with a pair of suitably sized fender-washers inserted within the spindle-shaft (and held in place near the ends, with two pairs of nuts), and also a larger-sized pair of fender-washers at the outside-ends.
__ Else-wise, keep the pinch-slots cleaned-out and (then) the pinch-screws re-snugged.


Dukaddy-Dukes,
DCT-Bob

[Eldert]

a widecase has M8 x 1 hex head pinch bolts . the narrow crankcases had M6 pichbolts

Eldert

[JimF]

Hi John,

That is a strange arrangement on your swing arm. Definitely it's not supposed to look like that. Without the bolts there you would normally see plastic caps to keep the dirt out and grease in.

There should be bushings in each end of the swing arm (bronze I think) and a steel pivot pin is then pushed in from one side until it seats into the bushing on the opposite side. There are grease fittings (at least on narrow case bikes) for greasing the pivot pin.

I am wondering if you have the pivot pin at all given that it looks like a bolt passes through. You might want to take it apart to see what the arrangement is, but maybe you want to wait until the riding season is over (if you trust that what you have is working well enough.)

I am no expert but let's say you take the swing arm off and you want to refurbish the bushings and get it all back to stock or normal or whatever... I think you would have to source the bushings and a pivot pin, have the bushings pressed in with a press and then have them line bored to accept the pin diameter.

I think Road and Race in Australia sources an over-sized swing arm pivot pin so that if you still have bushings but they are too worn you can line bore them for the over-sized pin diameter. Still though, for a guy like me anyway, getting it all taken apart and to the machine shop and then back home and then all back together again would put my bike out of commission for a good while which is why you might postpone it until you have nothing but time (the off-season.)

Jim

[Teckhardt]

Swingarm bushings:

http://www.guzzino.com/duswarmbu250.html

Swingarm shaft:

http://www.guzzino.com/swarnpishwc2.html