Back to getting the Bike Started (CB 125 TDC)

[richjp]

Hi all

Been a while, but now it's warmer and I have time at weekends again, I'm back to trying to get my Superdream 125 started.

I have fixed the problem with the starter clutch and bought a car battery to save stressing the bike battery.

Spent some time again today trying to get it started, but as reported last year, turns over, lots of 'phut, phut phut' and greyish smoke coming out of the exhaust ports on each 'phut' (running it without exhausts for the moment), but still not firing up.

I have checked the plug gaps and also that they are both sparking. As Mike suggested I swapped over the HT leads, but didn't make any difference. Petrol is getting into the carbs. Am not using the choke, just have it on full throttle.

Mike - you said something last year about "a good dose of neat petrol down each carb inlet", I wasn't quite sure how to go about that - the inlets already have the fuel lines going into them?

That apart, is there something else I should check? So close, but yet so far . . .

cheers
Richard

[Usher4566]

Stick some petrol in spark plug holes ?
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New cd200 benly owner

[richjp]

Thanks for the tip - I'll give it a go tomorrow and report back . . .

cheers
Richard

[Usher4566]

If it trys to ignite then you no you have a fuel delivery problem .
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New cd200 benly owner

[richjp]

Pretty sure it tried to fire after I put a bit of petrol in each spark plug hole, so maybe I need to strip the carb - fuel is running into it as if I disconnect the pipes I can see it flowing.

Anything in particular I should check? I believe the carbs were Ok when I got the bike and all I did when I rebuilt the engine was to take them off so not sure what could have gone wrong?

cheers
Richard

[Usher4566]

Is this twin carb ?
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New cd200 benly owner

[richjp]

Yes

[Teflon-Mike]

1/ No Petrol in tank, Old/Stale fuel in tank
2/ Water/Sediment at bottom of tank
3/ clogged tank-strainer (on top of fuel tap)
4/ clogged 'sediment-bowl' / sediment bowl screen (bottom of fuel tap)
5/ Fuel Tap. Clogged, or switched 'off' or on 'main' without enough fuel in tank to flow through 'main' take-off
6/ blocked, clogged, kinked or otherwise perversely routed fuel hose.
7/ after-market, 'in-line' fuel filter, causing obstruction, or air-lock to fuel flow
8/ Blocked carburettor fuel 'inlet'
9/ Stuck Needle Valve in float bowl.
10/ Blocked idle-jet
11/ blocked main jet
12/ blocked primary air-way
13/ inoperative/poorly adjusted. non functioning choke mechanism
14/ air-leak between carburettor & manifold
- Perished, cracked or split carb mounting rubber (very common, with people ripping carbs off without removing air-boxes first)
- gasket at manifold
- missing balence port screw
15/ air-filter / air inlet blocked or obstructed
16/ Engine not 'sucking'
- tappets far too wide (setting is I believe 0,025mm, not 0.25mm, and at 2.5mm valves probably wont even lift off seats!)
- cam timing out, broken rocker, misaligned rocker, variouse other engine maledies.

But I'd start by taking carbs off and cleaning the buggers; draining tank & looking at colour of petrol coming out, swill & clean tank & dry it, strip teh fuel tap & clean, then re-plumb with new hose.

TIP: go to a motorfactors & they will sell you nylon re-inforced CAR hose, thats about 10mm diameter, wont bend and is too thick to be any use. Get 6mm internal diameter PVC 'windscreen-washer' pipe or fish-tank pump hose. Discolours and hardens over about 3 years, but clear, you can see fuel and see its not full of rust through it, and it is easier to 'plumb' to the carbs.

TOP TIP> Double & tripple check choke flap operation. Maker sure that the connecting tank between teh two choke shafts is a tight fit (Use cable tie snipping to wedge it if needs be) make sure that both flaps are fully open at the same time, and be sure that the cable is attached to hold them open, or they wobble around and send mixture 'all funny'
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Fizzer Thou]

The exhaust pipes will help to give some back pressure.
And using the choke will aid starting,not using WOT (wide-open-throttle).
If the carbs have not been cleaned since you bought the bike,it would be a good idea.Pay particular attention to the air screws and primary jets,then the emulsion tube and main jets.
Check to make sure that the inlet manifold gaskets are secure.If they are broken or damaged,this could introduce too much air into the inlet during engine running and cause a mixture that was too weak for normal engine starting and running.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[Teflon-Mike]

fixer just reminded me; READ the book carefully, and set the needle heights and air mixture screws EXACTLY as stated.

Far too often found them screwed ALL the way in (well, we wouldn't want them falling out now, would we?!) and the bike a pig to start.

Needle also sits one notch DOWN from mid-point, so often set mid, on presumption.

AND, while you have the carb apart, check the jets when you clean them for the Keihin 'Star', denoting genuine jet and Kehin sizing.

spent MONTHS faffing with teh carbs on the Corporal, swapping different carbs on and off, using different bodies, different jets trying to get it to run cleanly... UNTIL I discovered a Mikuni 38 jet is an AWFUL lot bigger than a Keihin 38!

Put Keihin Star jets in; went for a test run, and SUDDENLY not only did it pick up its skirts and GO, it went all the way to 70, like a star!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[richjp]

cheers guys - lots to try for sure, but all reads as sound advice - I will tackle the carbs first.

So now I know what I'm doing Sunday! Will report back.

[bikenut]

:karma: hi dude,

all good info........

flywheel key intact ( as stater motor clutch repair done )......

good compression....may be low with all that fuel washing bores......thumb test.......plugs out cold engine ( it doesnt run! ) place thumb over s/plug hole and whizz engine over.....thumb blown off and hot........


original ign system for your engine??

clean plugs and fresh petrol, small amount of throttle and try again.

battery whizzes engine over fast enough?......neons for spark confirmation when plugs in and eng whizzing over?......

[richjp]

Hi guys

Quick status update after all your great advice:

- cleaned petrol tank (yuk!)
- cleaned and checked carbs (everything looked as it should be)
- new fuel hose
- new air filters

After a few minutes of it just being the same as before, I suddenly started getting a much louder 'pot pot' (that's exactly as it sounds). So there's a change/improvement, but still not quite getting there. I have had to stop while I charge the (car) battery I'm using.

I have checked I'm getting sparks OK and fuel looks clean and is running. Haven't checked the tappets - was hoping to avoid that if possible, but will perhaps try that next?

cheers
Rich

[Usher4566]

I would check tappets because mine was running shit on one .and I replaced carb and done tappets not had a problem since but don't no wat fixed it as done both jobs together but my tappets were out .and its such an easy job not half as bad as you think
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New cd200 benly owner

[Walloper]

[richjp]

Many thanks guys.

When I last checked it I thought it was a blue spark, but I'll take a look at the spark / ht leads again. I can do it at night in the shed too.

Before I took it on, the engine had run, but the previous owner had a mechanical problem with it which I believe I have fixed by rebuilding it (in fact I think it was the starter motor clutch in the end ) So I had assumed the CGIs (and ht leads) were still OK.

I'll also check the tappets though if the spark looks healthy.

Will update you asap!

cheers
Richard

[stinkwheel]

When mine had sat for a long time, it would never start off the button but would go pretty easily if I push started it. After it had started once, it would then go off the button.

Second gear, get some speed up then dump the clutch. If you're big and heavy enough, you'll probably be able to paddle it along in second until it catches and fires (or you pass out from heat exhaustion).

Worth a try anyway.

EDIT: For what it's worth, it's unlikely to be a CDI problem. It has two totally seperate CDI units and those bikes will start on one pot quite happily (in fact, I've never known one fire up on both cylinders at once from cold, one of them usually lags slightly). Both CDIs would have to have popped to stop it firing up.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[richjp]

Hi Guys

HT leads / spark are fine - nice blue spark in the plugs and no leaks on the leads when I tried running it last night.

The idea of jump starting it is a good one, except it's a pain for me as the bike is in the shed at the bottom of the garden and we have a lot of steps down to it - easy getting it down, not so easy getting it up - need to source a plank!

Might try the tappets next first though . . .

Again, will keep you posted.

cheers for the advice - appreciated
Richard

[Walloper]

Go to Halfords.
Buy a can of ether. (Easy Start).

Before cranking the engine give the inlet to the carburetors a heafty snort of ether. (A 1 second skoosh.)
If you use too much it pre-ignites and prevents the engine turning over on the starter.

This will probably start the engine. You can keep it running on ether by giving it a wee shist just before it dies. You will learn the knack.

If you can get it to run on ether and it continues to die without breathing the ether then you may have a fuel supply problem.

Another thing.

Do you know what happens if there is too much petrol getting to the combustion chamber?
If too much fuel it will be too rich to ignite. This is known as flooding.
To remedy a flooded engine.
Choke Off
Open the throttle wide.
Crank the engine over several times.
This pulls fresh air through the engine which should remove excess fuel mixture.

Start on full choke.
Crack the throttle open a tiny amount. Just off the idle position.
Turn the engine over.
When/If it fires continue with choke until the engine begins to splutter or races. Put the choke off and Robert is the man who is married to one of your parent's sisters.
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W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[richjp]

Good news - well partly anyway. I got it running on easystart - so I guess I know my engine rebuild was OK as it didn't explode . That makes me happy at least - been a long while coming, but I'm chuffed.

However, it doesn't keep running, so I assume that means although the ignition system is OK, I do have a fuel supply problem? A couple of weeks ago I had the carbs off and they seemed OK. I cleaned the fuel tank and put new pipes on, so not sure where to go next?

cheers
Richard

[Usher4566]

Hi how long is pipe going from fuel tank to carb ? Can u take pic of it .also if u undo drain screw at bottom of carb does fuel piss out ?
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New cd200 benly owner

[richjp]

will take pic in the morning and also try what you say about the drain screw - will report back . . .

[richjp]

Hi all

Seems now to be working (after a fashion I appreciate) without easystart! I have attached a short clip of starting up. I appreciate it sounds rough as f**k, but to me it's music to my ears as I rebuilt the engine from a complete dismantle and it's my first foray into mechanics.

It doesn't idle - I guess there's adjustments still to be done and runs roughly, but I just wanted to make sure its basically working before I move onto stage 2 - which is to now strip the whole bike down and rebuild everything (plus get some exhausts ). When I have done that I can worry about getting the engine humming, even if that means dismantling parts of it to get it smooth.

Many thanks to all of you who have helped over the past year and a bit - especially Mike who has been a constant source of sound advice- much appreciated .

cheers
Richard

[Usher4566]

No exhausts didn't help buddy .from what ime doing with my bike cd200 I would get the engine running and then do strip down .getting my engine running cost me a fair bit .plus I had all spray work done then I took tank on and off so many times doesn't do paint much good just my 2p
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New cd200 benly owner

[nightshaddow]

personally i would ignore all the "no exhaust" info you have been given if its going to run it will run exhaust or not

https://www.youtube.com/watch?v=4OgsJD_2XdQ&list=UUuDq7jqKauxvdAqtwZf7xdw&index=3&feature=plcp

this one was an engine freshly rebuilt and never been run

and this was an engine that other than a service has not had anything done to it in around 7 years when i took it out of another bike and sat it on the floor

https://www.youtube.com/watch?v=shcAnK4-0Jo&feature=channel&list=UL

prime candidate for rough running i have found with these considering the stage you are at, poorly balenced carbs get that sorted you should see a major improvement
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"WHAT DO YOU MEAN 100 MPH THATS IMPOSSIBLE Its chinese OFFICER."
Current rides CB 125 TDE(the next project) NS125RK ( now on the road ) CB125TDC (soon to be project 17) melody ( the nephews )