Two wheeled query

FunkyCowie

FunkyCowie

FunkyCowie

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31 Dec 2004
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Essex, UK
I have a Piaggio B125 just out of warranty. It just had an engine overhaul due to a bit of metal fall off near the spark plug that cost me £500, new head gasket, piston rings, etc (I like the ride which is why I was willing, one time, to spend this kind of money on it). To the point...

It seems to be missing about 5-7mph off the top end, which it was missing before it needed the work done and the mechanic (who is very trusted in my area) is a little baffled. He's cleaned the carberretta (SP?), done a small repair on the exhast (lose fixing which brought up about 5mph. All this started after I was caught out in a torrrential down pour resulting in me getting soaked an having to go through a lot of water, but nothing drastic. The scoot will reach about 57-58 on the flat (top speed 65) and feel like its restricting itself. If I hit a slight slope it will of course speed up and I can feel it cut back almost like dropping down a gear, then increase speed and drop down again. Its not hard to manage when riding but it concerns me... anyone have a clue what might be the cause?
 
If its just had a new piston and rings you shouldnt even know its missing 5-7 mph on the top end as you should be running it in.

Not a lot can wrong with rap backs that you can sort yourself, check the air filter isnt blocked, check you have a nice taut throttle cable and thats its opening all the way, if he's had the exhaust off it isnt blocked, mabye the fuelling is wrong, whip the plug out and check it isnt black, if it is, lean the mixture off.
 
I would think that because it's an auto and has the same engine and trans as my ET4 the drive belt needs changing. Mine starts losing power and top end as the belt gets worn and by 5000 miles it is completely knackered. I'm 6000 miles into this belt and the bike feels like it's on its last legs. Changing the belt makes it feel like new again though and all the rough take up of drive, juddering and lack of power goes away.

Also a good long fast run tends to blow the bugs out, but since you're probably running the engine in it might well be a bit tight until beds in.

Edit: Also worth checking is the sparkplug wire. It's a truly monumentally crap bit of greasy haired Italian design. Where the engine goes up and down on the suspension, the coil is fixed to the bodywork so the plug wire fatigues and breaks inside. Then you get a weak spark and the engine loses loads of power. Even better is the plug wire is GLUED in the coil so you have to replace the whole thing, not just the wire.
 
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The mechanic said to treat it like a baby for 300 miles or so, not to go over 45-50 (which I did... god thats painfull). Then to ease her up to full wack over about 50 miles. So the new bits should be bedded in nicely... so drive belt you say? maybe I`ll suggest that to the guy as its gone over 6000 miles.

EDIT: I managed to pick up a service manual off of the bay maybe I`ll have a little delve... can`t be much more complicated than a computer?
 
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Just to confirm... 300 miles to bed in would be enough right? Cos I`m starting to have concerns about this 'trusted' mechanic if he couldn`t figure out it could be the drive belt.
 
300 miles should be enough. Reading the manual will give you a shock, I've tried to service mine myself and it's a nightmare. Anything on the engine is a headache to do.

Yeah the 125 eats belts, should be changed every 5000 miles. Basically it rides in between two spring loaded tapered discs which is known as the variator. When the speed of the engine increases the two discs move together and push the belt up towards the top od the discs which accelerates the bike. When the belt wears down it gets narrower so doesn't ride all the way up to top part of the variator and top speed is affected. Mine will only do about 55 at the moment but top speed is as high as 70-75 when the belt is new.
 
Thanks... this really is starting to sound like the issue and from what Ive read in the manual is concurs, and surprisingly they rate the refitting of the drive belt as suitable for a noob with a little experience, might give it a shot :)
 
You'll need to get a strap-wrench or a chain-wrench from the car spares shop or you won't get the nut off the flywheel. They are normally used for undoing oil filters on cars but are just the right size for the flywheel on the bike. The screwdriver trick in the manual doesn't work very well if the nut is tight.
 
I just changed the belt on mine and I feel compelled to tell you it's not an easy job!!! Inside the transmission is also very different to what's in the manual. If you want I can talk you through it as I found a few dodges but you'll need a fairly broad flat bladed screwdriver with a good size handle to get hold of and a long breaker bar (18") or you won't get two of the nuts undone. Forget the strap wrench as it doesn't fit in the 125 as the flywheel is bigger. Took me about 3 hours including cleaning up and re-greasing the variator bits but the bike feels much better now.
 
did you have to remove any side panels... not sure how your ET4 panels fit around that area? On the B125 they are a pain to get off according to the mechanic. And a talk through would be handy :)
 
No probs. Yes I had to take the side panel off to get to it all, but not sure on your bike. Probably yes knowing Piaggio.

So side panel off, take the front off the airbox so you can get to the top bolts on the transmission cover, take out the airbox securing screws so you can pop the airbox off temporarily. Take the engine dipstick out, that is near the front of the trans casing, take the breather boot off the front and lever off the round plastic cap with the Piaggio logo at the back. There is a nut under there that is extremely tight and it's not in the manual, so this is where the chunky screwdriver and long breaker bar will be needed. Turn the nut and you'll see the clutch turning through any of the holes. Stick the screwdriver in one of the slots and start to turn the nut and the screwdriver will lock the clutch up, then lean on it with the breaker bar and undo it all the way.

Now loosen all the bolts around the outside of the trans casing, undo them all and pop the case off. The kickstart mech. may drop out but it just slides back into the casing and the prong goes between the two parts in the case, you'll see what I mean. You'll now see the variator at the front (which doubles up as the flywheel) and the clutch at the back. The clutch is heavily spring loaded and very different to the one in the manual and I couldn't work out how to get it apart but it never really wears out so don't worry.

To get the belt off you have to remove the nut on the variator which again is extremely tight. You might need to play about with the angle but using the big flat-bladed screwdriver wedge the tip between the teeth and the bottom of the casing. If you get it right, when you try to undo the nut it jams the screwdriver in and stops the flywheel turning. Don't go belting it with a clubhammer, jus use a very long bar on it and it comes undone as I think it is threadlocked.

Once it's undone make note of the order you take the parts off, they look different to the ones in the manual but are basically the same. Peel the belt out from the back bit by pulling the two parts apart as they are spring loaded. Clean out the inside of the variator where the rollers are with brake cleaner and grease the rollers up nicely. Slide the back of the variator and the sleeve back into place.

Putting the new belt on is a bit fiddly but I fed it into the back bit first, then got hold of the clutch and pulled the spring loaded part of the clutch open. This allowed me to pull the belt right forwards and it made putting the other half of the variator on a lot easier. Basically wedge the belt as far to the centre of the back plates as you can, then when you slide the front of the variator back on it is easier to get the parts back on the splines and partially do the nut up.

Once you've done that you can tighten the nut fully by wedging the screwdriver in the other side. I tightened both nuts up to 45 Nm with the torque wrench but that's just basically pretty damn tight.

I didn't bother cleaning out the casing as it just gets full of crud again, but I did clean up the kickstart mechanism and greased it because it's crap at the best of times and every little helps. Then you can put the case back on and re-assemble the rest of the bike.

Hope that is a good guide for you :cool:
 
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