Starting after rebuild

Excaliburs, New Yorks

Starting after rebuild

Postby Woolwich » 13 Dec 2017 12:59

Hi,
I have just completed a complete bike and engine rebuild of a 501 New York and am having trouble getting it to idle and run nicely.
The bike has been put back to factory settings, so the idle jet, pilot and main are all as best as I can gather standard (thanks Morini NL website).
The air filter and air box are standard Morini with the exception of the removal of a couple of the more restricting pieces of plastic, flower pot type thing etc as suggested by NLM.
Dynamic timing has been done by strobe and seems spot on. Spark is healthy.
I am using clear fuel line for the moment, so I can see it has no fuel restriction and the Float bowls are filling.
The bike will reluctantly start only with a feathering of the throttle. It will continue to idle at around 4000rpm only with both chokes on.Or without choke only with throttle, if I can catch just the right amount, even when thoroughly warm.
It appears to run happiest with both the mixture screw and idle stop almost all the way in, although to be honest the effect of adjusting the mixture screw is minimal. Attempts when running to turn the idle down always result in a stall around 3500rpm.
The carbs were thoroughly cleaned and rebuilt with new Dellorto service kits, everything appears unblocked.
I am aware of the mod that can be done to the timing strip on the magneto and although not adverse to the idea I feel I must be able to at least get the bike running ok before trying to perfect it.
The good news is that occaisionally for brief periods when using just the correct amount of throttle, the bike runs smoothly and sounds lovely, so I am not despondent just struggling for ideas to move forward. Any thoughts very gratefully received.
Thanks, Mark
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Re: Starting after rebuild

Postby Ming » 13 Dec 2017 14:16

Just an idea - do you have the vacuum ports on the carbs either blanked off or joined together? I had a rough-running problem on the 250 until I realized I hadn't reconnected them.
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Re: Starting after rebuild

Postby Woolwich » 13 Dec 2017 17:10

Yes, they are connected to a carb balancer at the moment. Previously I tried with them linked by some reasonably stout hose, I had heard that flimsy hose can collapse under vaccuum.
Thanks for the idea though, I am hopeful that it is something simple and daft.
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Re: Starting after rebuild

Postby corsaro chris » 14 Dec 2017 17:31

Throttle slides the wrong way around? Although this should result in the bike revving like mad - see this thread (this forum is searchable, so you can just type in your problem - in a couple of words - and then browse all the responses...);

http://morini-riders-club.com/forum/viewtopic.php?f=4&t=4596&p=23292&hilit=throttle+slides#p23292

Good fault-finding!

CC
"I'll use the Morini"
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Re: Starting after rebuild

Postby norbert » 14 Dec 2017 18:49

With the Dellorto 28 there is no way to mount the slides the wrong way. Are you sure that there is no extra air soaked about the area of the inlet rubbers between head and carburator? Give a bit of brake cleaner spray at idle over this region. If it rises you have a leak over there.

good luck
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Re: Starting after rebuild

Postby Woolwich » 15 Dec 2017 08:43

Thank you both.
So it might not be the throttle slides but the thread in the link was helpful in confirming the step in the ignition advance may give similar symptoms. Another vote for giving this a try.
Yes, I will definately recheck the intake rubbers for leaks. They were replaced with new so shouldnt be cracked or damaged but it would be wise to eliminate this early.

I got stuck into searching the forum in greater depth. A couple of gems jumped out. It seems that due to airbox mods, changes in fuel and possibly the ignition issue, factory settings for carbs are propably not much help as a place to start. A couple of guys over the years have suggested the carb set up used for their Excaliburs/Camels, so I think these would make a more useful datum to start with and tweek from there.

Cheers
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Re: Starting after rebuild

Postby MickeyMoto » 15 Dec 2017 22:55

When I installed my 501 in the 350 frame with standard air filter all I did was add larger jets (started at 108 now at 118). It started on choke but would not run without. In the end I just kept enrichening the mixture (air screww, whatever you want to call it) as it was obviously a no throttle problem and it finally ran on no choke when warm. Now idles reasonably reliably.

btw I have not touched the Kokusan flywheel. When closing the throttle in a higher gear it slows down to 2.5k and then settles but does not stop abruptly. Maybe with a light flywheel the revs would subside too rapidly? Knock it down a gear and it slows a bit more. I like the effect and find it suits my style.

Mike.
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Re: Starting after rebuild

Postby Ming » 16 Dec 2017 08:01

MickeyMoto wrote:... I have not touched the Kokusan flywheel...Mike.


I don't think I'd touch the Kokusan flywheel (If I had one) until I had the bike running as 'normal'. They are not easy to come by and once you've removed the metal required you can't put it back if that doesn't fix it.
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Re: Starting after rebuild

Postby Woolwich » 16 Apr 2018 15:56

Thanks again for the input. Apologies for the age in replying but first the starter motor died and then the starter clutch packed up before I had a chance to play with the jetting. Being philosophical I am glad to get any weak parts sorted before the bike is on the road.
Anyway finally with some trial and error we got there. Ignore the jetting Dellorto suggest and go large was the answer. I now have a bike that starts well and seems to run fine, although I am running in the engine so have not really revved hard yet.
The bike sailed through an MOT and I am waiting for its reg docs. In the brief ride to and fro the MOT station the bike behaved wonderfully. A little gem of a thing. I am thrilled to bits.
Thanks again to all who contribute here. It has been a really helpful rescource without which the job would have taken a whole lot longer.
Mark
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