MGX 21

[activpop]

I was at the MG dealer yesterday. I sat on the MGX just for kicks. I struggled to get that monster off the side stand. I couldn't believe the force it took. Not the bike for me.

[Gmc28]

i rented one of those large guzzi’s down near Joshua Tree a few years back, for a couple days of touring the park and other areas up north of there.  I enjoyed it, preferring it over the Harleys i had way back.  that said, they all fall into the same problematic category for me:  they are the best type of bikes for cruising down the big highways, which is exactly where i do NOT want to be on a bike, except to connect to other non-highway roads.  

[guzzler]

I remember taking a mates 1700 Kawasaki cruiser for a spin a few years ago and being a bit intimidated at the size of the bloody thing at first.Then when I wobbled outa the driveway looking for the footpegs behind me...It must have been a sight. I did get the hang of it after a few minutes acclimatisation but they're definitely not my cup o Darjeeling! Another thing was how such a big motor could feel like a bloody 250.....Any trace of character completely removed!

Cheers  

[guzzigary]

Fella in our small riding group picked up an MGX a couple years ago after a protracted search for a clean low mileage unit 

Cam chain tensioner failed,lunched the motor ,close to home thankfully 

Last I heard sitting under a cover in the back of his garage 

[pete roper]

This is the second or third time I’ve heard of camchain/tensioner related failures on an MGX 21. First one I heard about belonged to the bloke who runs Wildguzzi. It I believe actually snapped a camchain somehow trashing one side of the motor. It was rebuilt and from memory did something very similar again shortly after.

The story really frustrated me because ALL of the second generation Hi-Cam motors are essentiallt identical as far as the bits that spin and go up and down are concerned. The cooling system is plumbed very differently in the small port 1400 motors but the lubrication system,  which includes both the cam chain tensioner feeds, the under piston cooling sprays and the cam, tappet and cam bearing feeds is all identical to the 1200’s and the MGS is the same, identical, to the other 1400’s which are all much of a muchness.

Once the flat tappet fiasco was sorted out the motor was pretty much bulletproof. I’ve seen a few dropped valves but that is usually due to the valve timing being incorrect after rollerisation or lack of oil changes but other than that most problems are oil leaks and oil pressure and phase sensor failures.

What made these MGX’s fail really frustrates me because nobody seemed willing to dig into it! Shops just seemed to shrug and either replace the motor or just push the bike into a corner and forget about it. Something like that would have driven me batty! Fixing it is the least of the problem if you don’t know why it failed in the first place! There is no point in just rebuilding something after it has blown up like that unless you work out why because, oddly enough, if you don’t, the chances are it will just do it again! I’d have had at it like a dog at a bone but alas I never had the chance.
 

My best guess, and it really is a guess, is that there is some fault in the machining of the oil galleries in the crankcase in the rear wall of the timing chest. Unlike earlier motors the front main is a pressed in steel sleeve with a tri metal coating, it’s not designed to be replaced. I’m sure this system was adopted for cheapness of manufacture but the upshot is that oil delivery around that bearing to supply both it and the under piston sprays, the cam chain tensioner feeds and the front cam bearings and rocker/cambox feeds is done through a fairly complex system of drillings and machinings in the crankcase itself. The ‘Guess’ I’m making is that somehow or by something that main delivery gallery is somehow blocked or partially occluded preventing the tensioner plunger from priming properly and maybe starving the front cam bearing of oil and causing a potential cam seizure in the cambox. Sadly I’ll never get the chance to follow up on this hypothesis and nobody else is likely to want to so it will, no doubt, remain as one of those eternal mysteries that blacken the company’s name from time to time.

As it is I was never a fan of the ‘Small Port’ motor anyway. Too smooth and it seemed to have moved away from the bare bones ‘Engineering Purity’ I see in the Big Port 1200’s. That’s just my own bias though. That and the fact I think the 1400’s are huge, under suspended, overweight, tubs of shite of course! 

[Lucky Phil]

1 hour ago, pete roper said:

This is the second or third time I’ve heard of camchain/tensioner related failures on an MGX 21. First one I heard about belonged to the bloke who runs Wildguzzi. It I believe actually snapped a camchain somehow trashing one side of the motor. It was rebuilt and from memory did something very similar again shortly after.

The story really frustrated me because ALL of the second generation Hi-Cam motors are essentiallt identical as far as the bits that spin and go up and down are concerned. The cooling system is plumbed very differently in the small port 1400 motors but the lubrication system,  which includes both the cam chain tensioner feeds, the under piston cooling sprays and the cam, tappet and cam bearing feeds is all identical to the 1200’s and the MGS is the same, identical, to the other 1400’s which are all much of a muchness.

Once the flat tappet fiasco was sorted out the motor was pretty much bulletproof. I’ve seen a few dropped valves but that is usually due to the valve timing being incorrect after rollerisation or lack of oil changes but other than that most problems are oil leaks and oil pressure and phase sensor failures.

What made these MGX’s fail really frustrates me because nobody seemed willing to dig into it! Shops just seemed to shrug and either replace the motor or just push the bike into a corner and forget about it. Something like that would have driven me batty! Fixing it is the least of the problem if you don’t know why it failed in the first place! There is no point in just rebuilding something after it has blown up like that unless you work out why because, oddly enough, if you don’t, the chances are it will just do it again! I’d have had at it like a dog at a bone but alas I never had the chance.
 

My best guess, and it really is a guess, is that there is some fault in the machining of the oil galleries in the crankcase in the rear wall of the timing chest. Unlike earlier motors the front main is a pressed in steel sleeve with a tri metal coating, it’s not designed to be replaced. I’m sure this system was adopted for cheapness of manufacture but the upshot is that oil delivery around that bearing to supply both it and the under piston sprays, the cam chain tensioner feeds and the front cam bearings and rocker/cambox feeds is done through a fairly complex system of drillings and machinings in the crankcase itself. The ‘Guess’ I’m making is that somehow or by something that main delivery gallery is somehow blocked or partially occluded preventing the tensioner plunger from priming properly and maybe starving the front cam bearing of oil and causing a potential cam seizure in the cambox. Sadly I’ll never get the chance to follow up on this hypothesis and nobody else is likely to want to so it will, no doubt, remain as one of those eternal mysteries that blacken the company’s name from time to time.

As it is I was never a fan of the ‘Small Port’ motor anyway. Too smooth and it seemed to have moved away from the bare bones ‘Engineering Purity’ I see in the Big Port 1200’s. That’s just my own bias though. That and the fact I think the 1400’s are huge, under suspended, overweight, tubs of shite of course! 

About 25 years ago Pete  a mate of mine worked for the Australian Ducati importer and they had a SS in the workshop that on pre delivery wouldn't extinguish the LOP light. They pulled it down until they found that one of the crankcase galleries hadn't been drilled all the way through. They finished drilling it and replace the big end bearing which were actually fine but did it anyway and put it back together. That Ducati went all the way through post assembly testing and running and the engine on the Electric back drive rigs Ducati used in the day for 20 min before installing in a chassis with no oil pressure. The very same friend when he worked in Warranty for a large Japanese importer was also involved in an Australia wide recall along with a team from the factory in Japan for incompletely drilled oil galleries in the heads of one of their 250cc 4 stroke dirt bikes of the day. Un crate the bike, pull the head check for damage and replace with a new head if damage found or finish drilling the gallery and re assemble and re crate. The team went round Australia pulling new bikes apart for a month or so. I've got quite a few of these anecdotes after years of knowing people at importer level for several makes, lol. Broken drill bits on computerised machining stations is the usual reason.

So your hypothesis may well be true or at least worth investigating at the time.

Phil

 

Edited 5 hours ago by Lucky Phil

[audiomick]

1 hour ago, pete roper said:

What made these MGX’s fail really frustrates me because nobody seemed willing to dig into it! ...there is no point in just rebuilding something after it has blown up like that unless you work out why because, oddly enough, if you don’t, the chances are it will just do it again!

Pete, it seems we think alike. As far as I'm concerned, your attitude is exactly right.