Running in again

Well after last years fiasco, with the new JS piston and rod kit on a fresh rebuilt motor nipping up on the DS piston 1000km from home. I am now carefully going for short jaunts to bed her in. Went for the first decent spin this morning down the coast to Bald Hill in Sydney, a popular bike hang out. so far the engine felt great, with a few judicious squirts to ensure the rings bed, but not so much as to get her too hot. I tried to set up the carb fuel levels, as per the Amal site, if I get the fuel levels in their recomended range 4~6mm from the top of the bowl, my floats are way to high above the bowls and foul on the roof of the float bowl and flood. I comprimised with a float height of 50 thou above the float joint, the engine runs and idles like a watch of the Swiss variety, but the left carb floods when the engine is shut down. I wonder if the new stay up floats, float higher than the old full plastic type?
So I will let her cool down, go and do something with the kids for the afternoon and come back to it, for some float adjustments and general head torque checking etc tonight, then maybe a night run tomorrow night.

Cheers Richard

I found, at least on my early 750, the new recommended Amal float level with the stay-up floats is way to low, at least for mine. Couldn't even get a good tickle. I put them back to the original settings and seems to work fine. Forget the dimension.

Make sure your float needle is seating, not letting the bowl flood, do it off the bike on the bench. Also make sure your petcocks are not dripping. If you need pictures or procedures if things are leaking let me know, I did a thread on it and it's easy to rectify.

Dave
69S

Yes, and you must have newer viton tipped float needles, even these degrade after a few years and allow gas bypassing and overflowing,dripping.Gasoline attacks rubbers and plastics and these things have to be changed out every few years.A matter of course whether Amal or Japanese.

Well , what they pass of as gas nowadays , anyway .

Presumeably Either the Ignition or Carburation caused the trouble .

No point haveing the ignion the last notch possible fwd . ( advanced )
Running In .With the old manual advace set ups , like a ckoke lever on
the bars , you selected your required setting on the move , or well back
for starting . So a degree or three late on fireing at the lower rpms
more aplicable than melting it .

Normally ones very thurough in seeing the Carbuation is correct on a New Engine / top end overhaul or other than old dog .
Vearing toward RICH if establishing settings , i.e. needles up , Low choke cut off ( if varying slides ) and a size or two up
on the mainjets .
A overhauled engine may require differant settings to previous as its efficency is better , Sucking like a etc .

And , as people have pointed out , ' Published settings ' were for unadulterated Refined Fuel originally & apparently
a bias RICH from them is neccesary .So while it may be beating about the bush , at least your on the right side of it .

Also PLUGS play a part in ignition point . Hot plugs tending toward preignition .

Big check is if the centre electrode is not keeping its square edge , its over advanced . Combined with blistering / craterish
that & lean . blistering / cratering lean .

While exxcessive fuel would dilute oil eventually and tend to wash it out , thats extreeme ( Like Stuck Floats - wash )
Floats to low will induce leaness . Economy freaks would bias it there where its more gutless .
Power cowboys preferring the tad rich increase in tourque , which usually at full flow at top revs continuous comes spot on .

Stutter / miss type chimes in and backs of increaseing speed with the rich beat , idle , is lean indication .

deep Burrup burrup beat is bias rich .Useually a bit of black smoke thrown out throttleing up is FUEL / rich .
(white smokes oil )
Though weak ignition can give rich or both symptoms .

ALSO specific gravity of fuel now may be not the same , so require altered detail on setting level so as its ACTUALLY the right hight operateing . Observing the tide mark ( bamp line ) etc , where its not hot in the sun .

Keeping a bucket or two of water handy , & or a fire extinguisher isnt going to do any harm .

stockie2 said:

Well after last years fiasco, with the new JS piston and rod kit on a fresh rebuilt motor nipping up on the DS piston 1000km from home. I am now carefully going for short jaunts to bed her in. Went for the first decent spin this morning down the coast to Bald Hill in Sydney, a popular bike hang out. so far the engine felt great, with a few judicious squirts to ensure the rings bed, but not so much as to get her too hot. I tried to set up the carb fuel levels, as per the Amal site, if I get the fuel levels in their recomended range 4~6mm from the top of the bowl, my floats are way to high above the bowls and foul on the roof of the float bowl and flood. I comprimised with a float height of 50 thou above the float joint, the engine runs and idles like a watch of the Swiss variety, but the left carb floods when the engine is shut down. I wonder if the new stay up floats, float higher than the old full plastic type?
So I will let her cool down, go and do something with the kids for the afternoon and come back to it, for some float adjustments and general head torque checking etc tonight, then maybe a night run tomorrow night.

Cheers Richard

Click to expand...

If you have not been able to find out what caused your problems last year and rectified it, then its very possible the problem will occur again. Amal seem blissfully unaware of the fact that richer jetting is required for bikes running on modern fuels, and if you are running jetting intended for use with 5 star leaded fuels, this is something worth looking at. Timing needs to be carefully checked with a strobe light at full advance, making sure its advancing to factory spec figures. Cylinders which have been properly plateau honed by a skilled operator will need little "running in" especially so if you are using forged pistons with higher bore clearances than cast ones.

First thing to get right on carbs is the float level as everything else is based on that. The only way to know if that is right is best idle attained at 1.5 pilot screw turns out. No matter the state of tune 1.5 turns out is the base line to aim for by float level. If other than 1.5 turns out gives best idle you have to figure out why or suffer again later.

On initial run in on new cam ring sealing takes a back seat to holding rpm up long enough to bed in the lifters and rings should seal in a few minutes while cam can take like 20. You can't hardly over heat a Commando on un loaded throttle fuel burn amounts so not an issue to hold over 2000 rpm minutes a go to aid cam life.

Its also good to flush a new tranny rebuild oil after short break in too.

Stockie
Do you know what clearance your piston has in the bore. For Australian conditions you are generally better to have the maximum quoted clearance rather than the minimum especially if you are running in during the summer. In reality though you probably ran the bike too hard, too quickly. I would not attempt to run the bike flat out for at least 1000miles. I have rebuilt and run in many vintage bikes and some of them have felt so tight that I didn’t exceed 45mph for 1000 miles.
With regard to jetting your amals I would think that you would probably be running 95 or 98 octane unleaded as I would expect your compression to be over 9-1. If so you will be running too rich rather than too lean as advised by another who clearly has no idea about Australian fuels. You will find that you will have to reduce jet size by 10% to 15% on what was specified for leaded fuel. If you try Shell optimax you will have to reduce jet size even further. (try optimax in a Harley and see how fast it soots up a plug and it stops firing). E10 fuel requires similar jetting as leaded fuel used to. It doesn’t hurt to be a bit rich for run in so check your spark plug for colour and be guided by that.
I used to love the run from Sutherland down Bulli pass then up the coast road to bald hill then through the royal national park to loftus. I had many a run at over 100mph through the park. I remember one run with my mate on his GSX1100. I had my new girlfriend on the back of my Dunstall Commando. I ended up marrying her but it took me over 20 years before she would get on the back of a bike again.
Ando