Trouble starting hot?

**Motu** · 25th January 2015, 18:23

Starting singles is an art - I started on British singles, and being only 7 stone I had to learn technique as I had nothing else to back me up. Throttle only open a tad was important, just off the freeplay. Conversely, when I worked on stationary engines, they have to be set up to start on wide open throttle.

**jasonu** · 26th January 2015, 07:27

Originally Posted by Woodman

No major mods except its overbored to suit an xr280 piston, and some porting work and the compression has been raised to about 10.5:1. .?

Those sound like major mods to me.

**FJRider** · 26th January 2015, 17:05

Originally Posted by Woodman

T Has a very sooty pipe too ...

The unleaded fuels can cause that ...

**Woodman** · 26th January 2015, 20:13

Originally Posted by jasonu

Those sound like major mods to me.

Yeah, granted their are a few tweeks, now if I can only stop the clutch from randomly slipping I will be able to see how she will perform. The coil lead fell off yesterday just shy of 80mph (indicated) but hard to tell if the clutch was slipping or not.

Originally Posted by FJRider

The unleaded fuels can cause that ...

Yeah you are right.

**Grumph** · 30th January 2015, 06:08

Saw a similar problem on another pushrod single....it was lack of valve clearance when hot.
Given you've bumped the com up, it's going to run hotter anyway, so allow a tad more clearance.
These things have a weird setup where the oil goes up the pushrods too...

Your clutch problem could well be an indented basket. They're pretty soft. Clean up the slots with a good flat file.

**Woodman** · 19th July 2015, 17:03

Ok, back to this.

Got a bunch of jets and new needle and spent a bit of time jetting and set the points to the proper setting and set the ignition timing which was ok.

Bike starts and runs sweet. Pulls like a tractor, but misses at high speeds, maybe 5000rpm? (no tacho). Starts missing a wee bit then gets very bad.
Checked and redone all the connections in the ignition circuit and added another earth for good measure, but still misses. Coil and lead are new.

It has an adjustable main jet and I have experimented with that a fair bit today on the fly so pretty sure the miss isn't fuel related.
My understanding is that if it was the main jet being too small it would just stop revving and not miss? correct?

Magneto? coils? both 40 years old
Any ideas.

**Grumph** · 19th July 2015, 18:46

Either points bounce or just plain old age in the windings of the LT mag or coil.

Edit - memory came up with a Ducati mach one a few years back which had the same symptoms. Turned out it had an early points cam in which gave minimal dwell...6v plus modern fuel wasn't a very good combination. Lengthened the dwell by grinding, polished the cam to extend points life and much better.
Find a multimeter with a dwell function and check.

**Woodman** · 23rd July 2015, 05:46

Chur,

Coils. How do I test them? Anyone in NZ rewind them? any good place that sells them online? looked but can't find although they may be generic small italian ones so just may need to measure and compare to the few that I have seen on the internets.

Also , can the flywheel be remagnetised? have heard this can also be an issue. How do I test for unmagneticness?

cheers

Edit, BTW the clutch is good now. Was the springs. Now replaced.

**Grumph** · 23rd July 2015, 06:31

Originally Posted by Woodman

Chur,

Coils. How do I test them? Anyone in NZ rewind them? any good place that sells them online? looked but can't find although they may be generic small italian ones so just may need to measure and compare to the few that I have seen on the internets.

Also , can the flywheel be remagnetised? have heard this can also be an issue. How do I test for unmagneticness?

More detail needed. If you're referring to the low tension coils under the rotor, shouldn't need a rewind if they've still got continuity and insulation.
If the separate HT coil, something generic with the appropriate primary resistance will work.
Could be right about flywheel magnetism, they do go off with age. I'd ask one of the mag specialists who service the Classic register guys where to get it done.

**Woodman** · 23rd July 2015, 17:49

Originally Posted by Grumph

More detail needed. If you're referring to the low tension coils under the rotor, shouldn't need a rewind if they've still got continuity and insulation.
If the separate HT coil, something generic with the appropriate primary resistance will work.
Could be right about flywheel magnetism, they do go off with age. I'd ask one of the mag specialists who service the Classic register guys where to get it done.

Yeah sorry, the LT coil. They look fine, but will test. HT coil is new, and apparently right for this bike.

Would be good to find where to remagnetise cheers for the effort.

**Grumph** · 23rd July 2015, 19:18

Originally Posted by Woodman

Yeah sorry, the LT coil. They look fine, but will test. HT coil is new, and apparently right for this bike.

Would be good to find where to remagnetise cheers for the effort.

I know it can be done - just not who does it now. Used to be a place in ChCh where i had mags remagnetised - big impressive giant "G" clamp shaped lump which hummed and spat sparks....
I'm sure I've seen someone on here report having a rotor remagnetised - just can't remember who.

**Woodman** · 25th July 2015, 15:59

Took the flywheel off today. Seems to be pretty magnety and the coils look ok. Points were worn more than first thought so gave them a file. Will test ride soon as in my haste to go for a ride forgot to torque up the flywheel and the key got shorn/shawn/sean/sheared off as it sat there idling in the shed.

No damage, just need a new key so will have a poke around in the workshop at work tomorrow.

**pete-blen** · 25th July 2015, 20:04

Condenser...

**Daffyd** · 25th July 2015, 23:12

Take a small dry ice fire extinguisher with yo and give it a blast before you try to start it.

**Banditbandit** · 28th July 2015, 13:32

Originally Posted by husaberg

Pilot and idle too rich, will make starting hard when hot. The 7 plug is also likely too hot for a hotted up engine, my 2 cents. Neat bike those.
remember seeing one about 24 years ago at tommy McLeary's in chch

Yeah .. this

Originally Posted by Woodman

Just emembered that I had raised the needle the other day and it wasn't having those issues then. This bike has basically been in boxes since 1991ish. Bought it in Greymouth in 1982ish for $125 and rode it round their for a couple of years. Was bloody fun at the Taylorville kart track till they kicked us off.

It does run pretty hot. Food for thought.

Yeah - sounds like it's too rich ...

Originally Posted by Woodman

Took it for a longish ride today . ..., but starting was not an issue if I held the throttle open.

yeah .. holding the throttle open leans out the mixture ... it's too rich