Some rough running problems

[Daddy Dom]

Hi all,
I have just returned from the ride from hell on my 1983 Sport, right after having some work done. By the way, as I have no workspace whatsoever, I have to depend on local m/cycle mechanics. I will outline the story so far.

Last week I had some work done, including a new 'A' cambelt replacement and, afterwards, noticed there was a slight whirr/whining noise coming from "down there".
Question: is this normal until the belt gives a little, or should I be worried?

I also noticed they replaced 3.5 litres of engine oil, as directed by the handbook I'd given them. I'd forgotten to tell them it was 3 so drained off the difference.
Question: is 3 litres still the correct amount?

When they balanced my carbs I was also advised to fit new emulsion tubes and needles, which I did. The bike ran crisply and ticked over nicely.

Today I went for a shakedown ride (mostly between 4,000 and 7,000 rpm) but after about 40ks the rear cylinder started misbehaving, popping and straining below 5,000rpm - so, fine if I kept the revs high. At traffic lights and after filling up, lifting the choke lever seemed to help.

Then on the return journey I thought I could hear some odd noises beneath me but it was windy so I don't know what I was hearing. I carried on though at one point the popping got quite bad, the bike stuttered and the oil-pressure light went on for a second then stayed off.
I made it home smoothly keeping the revs high, and on my arrival it ticked over nicely, as if to mock me.

So I will check the plugs colour and both carbs later on in case something's blocked or loosened itself but other than that, HELP!

Thanks in advance,
Dom

[danomar]

I do not recall hearing a whirring noise ever from the cam belt. Are you sure yours requires the "A" size?

I thought the 3.5 sump holds only 2 litres. Maybe the later models had larger sumps?

The rear cylinder misfire could be several things. Usually a high-rev miss can be attributed to deteriorating spark (often the result of heat affecting related electric components) or fuel delivery problems—often a stuck or incorrectly set carburetor float. You mention the choke helped, so I would guess that there is something preventing enough fuel getting through at high speeds. It is easy to overlook a small piece of dirt.

HTH

[stillooking]

for oil level, see this link

http://www.motomoriniclub.nl/tabel.html

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Re. the belt, wouldn't have thought it was normal to hear unusually loud running of the belt. Normally, I hear the clatter of the tappets more than anything. Where did you get the 'A' belt from? - there's been a lot of correspondence over the years about what's suitable and what's not. I won't repeat what's been said but...just have a look on Google and this website etc and also the Dutch website above.

I'm using a std Gates industrial one. It doesn't have a 'tolerance' fitting vis a vis A,B, C etc. So far so good, it's been in the bike for 4 years (but not a lot of miles).

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re.engine/carb problems, wouldn't like to guess, so perhaps someone else can assist?

[EVguru]

Does it still have the electric fuel tap?

They're notorious for not giving enough fuel flow at sustained speeds. Mine mostly works, but sometimes is just 'moody' and I need to open the manual tap too. One very anoying sympton is riding along just fine at around 50mph, then pulling up at a junctiona and having the engine just quit. The main jet is at the bottom of the float bowl, whilst the idle jet is near the top. If I know I'm getting low on fuel I'll roll off the throttle and back on to see if there's a hesitation at low throttle (idle circuit).

[Daddy Dom]

Thanks for the replies.
Yes, I am replacing an 'A' belt with another. It's a Morini one sourced from NZ's Morini racing team, Strega Racing.

Yes, EV, I am on the electric tap but the problem first presented while on reserve. I automatically think that's a dangerous time as any dirt in the tank will be most likely to present itself then but I couldn't find a blockage.

Yesterday it became apparent that the rear pot is cutting in and out but there seemed to be a strong spark when the plug was rested on the head. That said, the cylinder was definitely way cooler.

On a hunch, I may look at the wiring under the tank, which has been getting moved about each time I remove the tank. A headlight wire recently severed itself under there so it's worth a try.

As they say, "most carburation problems are electrical". Even so, I am thinking of having the carbs ultrasound-cleaned even though they've just been balanced. Oh well. Can't hurt.

Thanks all,
DD

[Daddy Dom]

I have two new grey transducers coming so will see how that works out.
Cheers all,
DD

[Daddy Dom]

Fire in the hole!
My 1983 triple disc Sport, K23313, has burst into life once again. (Touch wood, fingers crossed and a rabbit's foot.)

The culprit was a dead (grey) transducer. Following a mercy-call to my local source, he left a pair of new ones for me the day before going on a riding holiday to Europe (thanks, John!). Frustratingly, they were the wrong type so I bit the bullet and ordered a brand-new NLM transducer kit. More than a week's wages for poor me. After a little stuttering start from standing a month, she seems all fine including an exploratory 3k ride before work this AM, and before more rain would have made putting things back together impossible.

A note to anyone else ordering these - apparently the last batch were incorrectly wired and what is described in the instructions as a brown wire (shorter loom) and a black one (longer loom) are actually coloured the other way around (thanks Alex!). You'll also need a spacer or bunch of washers between the coil mounting-plate (LHS) and the mounting bracket to clear the airbox and finally, the blue earth wire will need liberating from the sheath it shares with the other leads in order to reach the frame. I bolted it to an airbox mount.

My whirring cambelt no longer does and I no longer care that it has been raining in Auckland for almost a month, I'm going out for a ride.


....damned carbs ....