Noise and hunting after changing rollers and belt

[Didediedide]

G'Day All, My 2008 250ie xevo has now completed 20000 km and it was time to change the drive belt, I didn't do the job myself but had a motor bike mechanic do the job, when he opened the case he said the rollers should be replaced also when I got it back there was a horrible rattle which seemed to be coming from the clutch area so they pulled it apart and couldn't find any thing wrong and put it back together again the noise was still there and it was reduced to an acceptable level by increasing the idle speed from1800 to 2100rpm and was told the noise would settle down. When I got home and checked on the net to a reason for the rattle I read about the fact that the rollers should be installed in the correct orientation so thinking that may be the cause (mechanic didn't know they had to go in a certain way) it came apart again sure enough some were right and some were wrong after this was rectified the noise never changed.Now I notice the engine is hunting at idle from the 2100 rpm (no or little noise) down to 1700 rpm (noise reoccurs) then after a few seconds up to 2100 .This hunting was not occurring prior to changing the belt and rollers any body got any ideas to a possible cause for the rattle and the hunting at idle ( the mechanic is blaming the fuel injection but I doubt it seeing it never happened prior to the work being done) to me seeing the noise seems to be coming from the clutch end of the case is it probable something in there is loading the engine up (reducing the revs ) and then letting go Regards from Aus Paul

[roadster]

 I agree that it is almost certain something has been damaged or incorrectly reassembled. Are you sure that the correct parts were used? Its worth checking the part numbers. Hiding the problem by increasing the idle speed is totally unacceptable. It is possible to run the engine with the case removed to try to establish where the noise is coming from but the snag is that if your model has a clutch outrigger bearing in the case it might not be representative. Speaking of which is it possible that the washers or spacers on the clutch shaft may have been misplaced! The assembly order needs to be carefully checked against the manual and/or or parts book.

Regards Roadster

[Dave Milnes]

Certainly sounds like something has not been fitted correctly. Increasing the idle to such an amount may be causing the clutch to slightly engage which will slow down the engine, so it releases, the idle speeds up and the cycle begins again.
This also begs the question as to how the idle speed was increased on an Fi engine. It should NEVER EVER be done using the throttle stop screw on the throttle body and only be done via the diagnostic tuning kit and the ECU settings.
Rollers do have a correct orientation but incorrect fitting doesn't usually produce noise, just greater wear on the variator itself. Again though what rollers are now fitted, proper OEM ones or cheap after market items? Only OEM or possibly Dr Pulley ones are worth using. Forget Malossi or Polini etc unless you are using a complete variator from them, as their rollers may not be the correct length or diameter even if they are the right weight for a stock variator.
Often when changing belts and rollers the sound is different initially but does 99.9% of the time settle to normal after a few hours riding. It should never be described as rattling after changing, but can get a bit noisy before changing.
In all honesty I wouldn't have changed the rollers at a mere 12,000 miles, they will last 2 or even 3 belts although a visual inspection looking for distinct flat spots is the ultimate indicator.

[Didediedide]

Thanks Roadster and Dave for your responses, Dave guess what the mechanic turned to adjust the idle speed yea your right that little throttle stop screw now I can't seem to get it adjusted in the correct position but I think that May be the thing that is causing the hunting. I believe he used genuine rollers (so I was told ) but a genuine belt was not used he used a Dayco. Would a decent piaggio mechanic be able to re adjust the throttle stop screw to the factory setting to get the fuel mapping back to where it should be using a diagnostic tool Regards Paul

[roadster]

Thanks Roadster and Dave for your responses, Dave guess what the mechanic turned to adjust the idle speed yea your right that little throttle stop screw now I can't seem to get it adjusted in the correct position but I think that May be the thing that is causing the hunting. I believe he used genuine rollers (so I was told ) but a genuine belt was not used he used a Dayco. Would a decent piaggio mechanic be able to re adjust the throttle stop screw to the factory setting to get the fuel mapping back to where it should be using a diagnostic tool Regards Paul

The throttle stop screw is a matter of mechanical adjustment which provides enough butterfly clearance to prevent the butterfly becoming stuck in or damaging the throttle body yet without allowing more than a very small amount of air to bypass the electronic idle air control system. The secret is that after setting and locking the stop screw the throttle position sensor must be recalibrated to match. This is done using the diagnostic tool and is known as a TPS reset.
In practical terms you might get away with returning the stop screw to its previous position and judging this by matching the idle speed to what it was previously since this is probably the only realistic way of measuring the air flow through the butterfly.

[Didediedide]

Thanks again Roadster, I think I have the screw set close to where it was before and now I will have to find a mechanic who knows what he's doing and see if I can get the TPS set correctly. even though the idle seems better its still not right and it seems to be using a bit more fuel than normal Regards Paul

[Dave Milnes]

Really you need a new throttle body followed by a TPS reset via the diagnostic device, the only time this is ever performed. It's in the manual never to touch the throttle stop screw. The balance of fuel to air is set at idle and if the butterfly is letting air past as well as the air bypass valve, the ECU cannot get a proper adjustment so it will be out across the range as the TPS sensor has an incorrect base position.

If the stop screw is backed off totally so the butterfly is tight shut, the idle should be stabilise and be correct but the butterfly might tend to stick in this closed position if the throttle is allowed to slam shut so the stop screw needs adjusting so that there is a microscopic clearance of the butterfly lip from the body and no more. The ECU should then control idle via the air bypass valve and the mixture be correct again. Worth a try.

[Didediedide]

Thanks Again Dave for your interest and help, I have been fiddling with the adjustment screw and you are right only a very minor movement of the screw is required to make a change to the way it runs ,I hope it doesn't mean a new throttle body that sounds expensive. The "EXPERT MECHANIC" that moved the screw in the first place said not moving the screw is b... S... I've done that hundreds of times, I went to this bloke thinking I was saving money but I've ended up with nothing but trouble .I should have had a go doing the belts and rollers my self it doesn't look too hard. Could you please inform me to a link to down load a work shop manual for the 250ie xevo I'm sure there must be plenty of jobs you could do yourself ,save some money and learn a bit at the same time Thank you very much once again Paul

[Dave Milnes]

There isn't as yet a specific manual for the Xevo 250 but there is an MP3ie manual which covers the engine and transmission good enough to do normal servicing.
http://www.wotmeworry.org.uk/manuals/Piaggio%20MP3/MP3%20250/MP3%20250%20Workshop%20Manual.pdf

The trouble with some bike mechanics is that they assume modern scooters are still old fashioned and you can treat them like a classic bike as opposed to a modern one.
The way such manufacturers as Piaggio protect their manuals doesn't help either as they haven't access to the info needed.

[Didediedide]

G'day Dave, I have down loaded the manual thanks very much, I seem to have the butterfly adjustment screw back into the correct position or at least close to it, the hunting has been almost rectified , I haven't gone any further re getting the throttle position sensor adjusted using the diagnostic tool. This morning I had an offer from a member of the Australian scooter community Mr Mike Holland, Mike has had a lot of experience with Vespas and he said If I wished to ride down to Sydney he would have a look at the rattling problem for me. So this morning I took of for Sydney 100miles south of Newcastle ( it hasn't rained in Newcastle for 2 or 3 months guess what it did for the first 30miles this morning) any way when I arrived at Mikes home he listened to the noise (no where as bad now as it was) and pulled the drive apart for me everything appeared normal and he believes the thing that need to be done is install Dr Pulley sliders (I will have to check with him again but I think it was 21x17 x 11grams) Thanks for the interest shown by all concerned Paul   

[Dave Milnes]

If you want to improve performance go 10% lighter on Dr Pulleys than stock rollers. This will give a bit quicker take off but not effect top speed or economy. Dr Pulleys will last years, probably as long as you own the bike. They are much tougher even than the original rollers so if increasing performance isn't required, consider them a 'fit and forget' type of upgrade.