Advice needed for a non-starter

I’m finishing off the restoration of a 1997 grey import Honda CD125t Benly that I intend to commute to work on. It’s the one that looks a bit retro that you can see people from Korea and Sri-Lanka riding on YouTube with the full mudguards and black paintwork. I've owned it for twenty years but its been out of use since 2003.

It was running but kept stalling before restoration.

I had to take the head off for welding (top mounting lug broke off and was left attached to the top frame mounting bracket, spark plug thread all mashed up.

After re-assembly the engine had a big fat spark and fuel, turned over freely but refused to start. I checked several times and the timing was spot on.

So I gave up and bought a CB125T second hand engine off of eBay (seller assured me that it was running okay and I do believe him)

However, the wiring for the stator on the new engine was different (fewer wires and different colours plus the wires had been cut off from the frame really short) so I simply fitted my original stator and rotor onto the replacement engine and plugged it in.

Ready to go… except not.

I have the same problem- fuel , spark and spot on timing yet turns over and won’t start.

What have I missed? Is there any way to test the pulse generator? Would the trigger for the pulse generator be in a different point on the original rotor compared with the one that came with the engine?

Anyone got any ideas?

You could try a load of easy start see if that helps, but if the pulse generator was different that's where I'd start looking

You could try a load of easy start see if that helps, but if the pulse generator was different that's where I'd start looking

But it did the same with the existing engine in,if it has spark air and fuel it should fire

You could try a load of easy start see if that helps, but if the pulse generator was different that's where I'd start looking

 

But it did the same with the existing engine in,if it has spark air and fuel it should fire

But is it only getting fuel into the carb and none out of the carb

Ie fuel at carb end of pipe but blocked/gummed float needle or jets

Does the plug get wet ?

Has the engine got compression?

Myself would not use easystart as not a fan of it but i am more than happy to use a drop of fuel direct through carb whilst others are not .

The bike has been out of use for thirteen years and you haven't made any mention of the carburettor yet. The first thing I would do is a full strip down and inspection long before I started buying new engines . Remove all the jets , inspect and clean as necessary , blow through all airways , replace the float needle , polish the float valve seat with Solvol and a cotton bud , inspect and adjust the float height and ensure that the choke and slide are functioning correctly . You've put the same carb on another engine and there's still a problem . Well that points the finger firmly at the carb in my book . Oh yea , I presume you are using new petrol .

My original engine would not idle .When I stripped down the carb I found that the tiny holes in the jets were all blocked up so I did an overhaul.

With the replacement carb that came with the second hand engine, the engine would not fire and it leaked badly ( I assume something like a stuck needle valve in the float chamber ) .

So on the basis that both carbs looked identical I put the original/overhauled carb onto the second hand engine to see if it would start - no leaks now but still no starting. I did resort to some easy start but to be honest if the engine won't fire on nice new fuel, its not right yet.

I know nothing about bikes really- can someone tell me if the pulse generator could generate a spark when tested but not somehow under load when connected up?

Yes by the way the fuel is new- the fuel in the tank when I started was a nice brown with bits of rust in it.

Thankyou to everyone who has replied by the way- it is appreciated.

You need the carb cleaning really really well after being stood for that long, ultrasonic tank is best you can’t get all the gummy old stale petrol out of the really small jets, the thing with the easy start is to prove the bike will fire up that the rules out the spark being the problem and places the problem most likely with fuelling issues.

As a quick test you could take the spark plugs out and dribble a small bit of petrol directly into the cylinders. Then try to start it. Making sure you have a good battery that's charged and your air filter isn't blocked. It should start and run for a few seconds on the petrol you just dribbled in. If it does start then that confirms the spark and timing are good and it would point to a fuel problem.

Over the past two days I've rebuilt my original carb and this evening fitted it to my replacement engine.

Before starting it up I took the plugs out. both were really rusty and caked in dirt. One plug had a damaged thread and what looks like a hellicoil fitted in the head. With plugs refitted I cranked the engine over several times and still had no ignition.

Adding insult to injury the engine started to pour oil out badly between the block and the outer casing and the screw and lock nut that tension the cam chain tensioner was rocking backwards and forwards as the engine turned over.

Beginning to suspect that the running engine is in fact a bit of a lemon.

As I wanted a reliable commuter, I'm going to bite the bullet and order a kit of parts and get the original engine overhauled properly and then see if I can get a new carburettor to finish the job off.

Sometimes you end up spending more time and money doing things on the cheap than you do if you do things properly.

Over the past two days I've rebuilt my original carb and this evening fitted it to my replacement engine.

Before starting it up I took the plugs out. both were really rusty and caked in dirt. One plug had a damaged thread and what looks like a hellicoil fitted in the head. With plugs refitted I cranked the engine over several times and still had no ignition.

Adding insult to injury the engine started to pour oil out badly between the block and the outer casing and the screw and lock nut that tension the cam chain tensioner was rocking backwards and forwards as the engine turned over.

Beginning to suspect that the running engine is in fact a bit of a lemon.

As I wanted a reliable commuter, I'm going to bite the bullet and order a kit of parts and get the original engine overhauled properly and then see if I can get a new carburettor to finish the job off.

Sometimes you end up spending more time and money doing things on the cheap than you do if you do things properly.

Do you have a reputable mechanic for the overhaul or are you going to be doing it yourself ?

Planning to order a kit of parts and then hand the engine over to someone who knows Hondas better than I do.

Sounds like the cam chain tensioner on the new engine is loose and or it's missing the copper sealing washer to stop oil coming out. That's not good because the slack cam chain might have slipped on the cam shaft. That can cause the valves to hit the pistons. If the seller said it was a good running engine you could probably ask for your money back