first rebuild fire-up advice please!

[Andie]

Hello - I'm almost ready to kick over my rebuild for Easter - The leggies are a few weeks off from completion, so back brake isn't fitted but ready to go...

Its been a complete rebuild - new GP crank, Rimini Iron 175 top-end, sliding dog + clutch plates, chain + guide, Casatronic 12v. Electrics checked with meter and a good spark present.

I've triple checked the carb (Jetex with replacement A/S jets, although the existing ones were stamped) 50 choke, 45 pilot and 118 main + new type 2 atomiser. mix screw out 3/4 from as far as mixture screw goes in with spring on. Crank case oil topped up.

However, when I come to put some fuel in and kick the block over, should I be aware of anything special? Or do I just go for it?

MB guide says get it ticking over on the stand for 30mins to bed in, which sounds like good advice.

Semi-synthetic PP2 rock oil, I'll be 4 per cent, my garage is Shell so super unleaded....

Any advice from veteran rebuliders gratefully accepted!

Thanks - Andrew

[CHRIS in MARGATE]

Wear a sturdy pair of trainers in case you have to bump it.

After a couple of minutes running just blip the throttle a couple of times to make sure it comes back to tick over. If it races then the mixture is weak and should be addressed promptly.

[Andie]

Thank you Chris.

Out to enrich and In to weaken the mix.

Fingers crossed for tomorrow!

[citydaz]

4% semi synthetic?
I used 3% fully synthetic after my mugello 186 rebuild.
just wondering what your logic was for this.
I was also advised to use 4% fully mineral as this would generate a degree of abrasion which would aid bedding in, fully synthetic being "too slippery".!?

[Andie]

4% semi synthetic?
I used 3% fully synthetic after my mugello 186 rebuild.
just wondering what your logic was for this.
I was also advised to use 4% fully mineral as this would generate a degree of abrasion which would aid bedding in, fully synthetic being "too slippery".!?

Thanks Daz this is where i sometimes get a bit lost with modern scootering.

When I was last running lambrettas (late 80's..) I never did a full rebuild and just put in 4 star and 4% '2 stroke oil' from the garage.

I'm happy to source better oil if it suits. My rebuild isn't tuned or posh in any way, quite standard.

Andrew

[ToBoldlyGo]

I'd use regular fuel. Super unleaded is full of detergents designed to clean up the engine. Possibly not a good idea if you're trying to get it to bed in.

Oh, and treat yourself to some Rock Oil Groundsman. Same stuff, but cheaper.

[CHRIS in MARGATE]

BP, Shell, Texaco Super Unleaded or High Octane is the fuel to use unless you have retarded the ignition.
Oil...IMHO ...No scientific data to support any of the many varied supporters' preferences. Oil snobbery !

[citydaz]

I agree - oil snobbery.
Theres loads of different advice and opinion, just go with what you feel comfortable with.
me personally I use silkolene competition 2 plus at 3% and never had a problem with running in my mugello

[Andie]

Hello

I've spent the best part of the last two days working on my build.

EDIT I'm not doing very well. can't get it to run for more than 20 seconds.... /EDIT

I've fuelled with BP 97 and 4 p/c semi-synthetic Rock oil. I was advised 4 p/c by the mechanic who built it, who knows his stuff.
Crank case oil checked with scoot level, off stand, and all good. petrol mix getting through to carb fine.
No ignition, just a kill switch that is working fine according to my meter.

1) spark

Its a casatrionic kit fitted to 19 degrees. B7ES Plug gapped at .5
Its not amazingly bright blue but its quite sunny outside.

The kit earths direct to the stator - I could fit a secondary earth from the regulator but it's CDI is earthing fine (black wire to frame).

The plug is wet and has a slight black oily sheen to it ( too rich a mixture?)

I have changed plug and plug cap (all brand new)

2) Petrol/Carb

Carb is a jetex 22 (200cc model) Jets are replacements - 5899-2 atomiser - 45 pilot, 118 main
I've started with the mix screw at 3/4 as recommended by my mechanic.

It won't start from kick over. - I managed to bump start a few times yesterday (i live on a big hill, hard up, easy down...)
It will fire with some throttle to get it to pick up (possible 1/8th + ) - choke in. Fires regularly and does not stutter

It wont tick over when bumped and clutch in without some throttle I've varied the screw from 1/2 in to 1 1/2 out but not much difference.
Could my pilot be too big?

Its flooding and the standard air hose, is getting a lot of spit back fuel in so today I cleaned the carb, and blew through jets with air-in-a can and carb cleaner. Float works fine - moves freely and blocks intake on up position.

The choke jet falls correctly and then clears the chamber so the choke cable seems fine.


3)Compression
Lots of compression! I also dropped the engine down today and checked the inlet (fine) and exhaust studs as they were leaking some specks of black petrol (same as plug). Torqued as the book although I can't get a socket to the flywheel side (U bend won't allow it). no longer leaking. The u-bend and box weren't the best of mates (AF Clubman) and it was also blowing black petrol/oil from the U-bend/box join but I've played around with the clamp and seem to have fixed that.

It bumped again a few times today but not much better. Plug still fouling. Smoke is fairly white but it has been flooding.

It sounds good - like a non too noisy clubman should.

My initial though is that I'm maybe over-jetted (its a 175, with stomach removed from airbox. standard seat, air intake has been cut away) and the mixture is too rich.
I could drill some holes in the airbox if neccesary.


Any advice kindly appreciated!

[rossclark]

Have you tried with the air hose off?

[CHRIS in MARGATE]

What happens when you put the choke on, does it stall or keep running without change to engine sound ?

[Andie]

Thanks - I've only got it firing by bumping in 2nd it fires up, quite quickly - choke out, then needs a lot of throttle (approaching a quarter - I don't want to over-rev as its not bedded in yet)to maintain a sort of tick-over that then gives out after a ten seconds. However when I rev it comes down easily.

By the time I've reached down to flip the choke down (or get into neutral so as to stop, dismount and check carb) it has died - have started some 2 dozen times. Apologies for not being able to explain fully without video. I've had to adjust, re-bump and deflood, so not brilliantly scientific on my part.

Edit - sorry Chris, what would the choke signify please? would it be a too rich mix pointer? I'm not an expert on carbs / Edit

I tried kicking without the air filter but not bumping.might be worth a go?

Tomorrow I will strip the carb again and double check the float mechanism and bouyancy and float jet and choke plunger.
Checked my reciepts and i didn't replace the choke jet or plunger...

I'm confident/hopefull that it's a carb problem, but will multi-meter the black and green CDI leads again. As the engine was rebuild elsewhere and then I fitted it, the stator might not be perfect, as its not been strobed, but I thought it would be fine and then once running I could get it set-up as perfect.

[CHRIS in MARGATE]

The choke richens the fuel mixture. If operating the choke makes little difference then the engine is running weak. If operating the choke causes the engine to splutter then the mixture is probably close to where it should be and the choke is making it too rich.
To simplify: Put choke on when running and no difference... BAD

Put choke on when engine running and then engine splutters and shudders to a halt ....GOOD.

You may have to do a leak test if carb is fine and electrics check out. Get a new bicycle inner tube and cut on half opposite valve. Make an airtight seal with one end around inlet manifold and the same with other end around the downpipe (exhaust disconnected).
Pressurise with a foot pump with gauge to about 7psi and watch to see if pressure holds. If not soapy water everywhere to look for tell tale bubbles.

[Andie]

Thank you Chris.

The choke should run at 50, turn it off and then just the pilot takes over, and runs at 45. Got it.

I have a new bike tube and decent pump with gauge and will check that tomorow. Thank you for your time and help!

Andrew

[Mark ULC]

Double check resistance of stator wires. Sounds similar to a LT fault I had. Good luck.

[missing lynx]

I may have missed something but you say "the stators not been strobed" if so how do you know the timings right? and most the jetex's I've set require the air screw to be some were between 1 and 2 turns out

[Scooter Paul]

missing lynx's comments are valid. If you're using an electronic ignition don't rely on the flywheel/ pickup marks. Use a strobe to confirm your settings. BUT, all your comments point to the carb flooding. Jetex carbs can work really well especially as you've used Delorto jets but some have issues with the float not pivoting freely on the pin this can cause starvation or flooding depending on where it's sticking. A little cleaning up with a file on the pivot tabs and reaming out the float pin hole with a drill bit will sort it. Whilst you're in there check the float needle is able to cut off the fuel flow and it's not perished or not seating properly. Good luck.
Paul.

[CHRIS in MARGATE]

Pick up the Jetex and blow through the inlet and as you do this lift the float and let it fall back on its own. You should feel and hear the needle shutting off flow as you lift and then allowing it when you let it fall.
Make sure you have gapped plug with correct feelers Imperial or metric ?.
Never wind the throttle back when starting. It will flood.

You need 3 elements to run: ignition, so satisfy yourself that everything is absolutely perfect; timing can come later. Fuel...Make sure carb is clean and allows fuel to flow. Compression....No air leaks.
I guess you need a 4th element: Luck !!

[rossclark]

Another way to check the float / needle operation is to remove the float bowl, hold the float up lightly with your finger and turn the petrol tap on. You shouldn't get any petrol leakage. If it does then you have a problem with the needle or needle seat.

[Warkton Tornado No.1]

Various contributors suggest carburetion as seems quite likely

Nonetheless, if the strobe you intend to use is a mains or battery powered version (most are) you should be able to check your timing by spinning the back wheel with the plug out.

That should tell you if you are in the right ball park.

You might need the help of another pair of hands, or, with caution, you may have an electric drill to which a 27 mm AF hexagon socket may be fitted to power the back wheel.

I’ve even done a similar check with a 17 mm AF hexagon socket on the flywheel nut but again, I must stress caution as the clockwise rotation would be attempting to loosen the nut. However, the advantage is that the gearbox will not have to be part of the load as the check is done in neutral.