Three years later, still having problems with idle

[mbmm350s]

Do the club still have a tool hire scheme

We don't any more - but these days quality tools can be obtained either from Mdina Italia or Tim Ralph (Ralph restorations)

It is possible to remove the rods without dismantling the crankcases and properly torque them after,
Chris at Lusso has done this, but this is only any use if the crank journal is good.
I have some early rods with deep wear on the sides where the two rods touch each other, for me its essential to measure the
side to side play and the straightness of the rod. It does look like the piston has pushed the small end bush over.
I cant see from the picture if the oil hole in the top of the bush is open.
One thing its not normal for the conrod to stay standing up as in the picture though i suppose it could be balanced there
- like they normally flop about and are free to move in rotation. I had this when someone hadn't relieved the radius and stiffness is bad,
it may have caused premature seizure of the piston i don't know for sure.

Mark

[George 350]

Hi,
I have looked at this picture and can't help thinking that the conrod isn't straight, but twisted slightly? I can see the bush is no longer central, but is it just the camera angle that makes the sides not look parallel to a line between the studs. If it is, it would explain your piston issues.
George.

[72degrees]

I thought that. Perhaps the side play is so much that it allows the rod to adopt that 'twist'. But these days it could well be my eyes

[Kamel]

Sorry to see this Long_Road, now I feel guilty for mentioning the "Tinkling" but I suppose it was already too late by that stage. The small end is definitely twisted anti-clockwise by a few degrees. Can the you see if the rod has twisted, or has there been a catastrophic failure of the big end ? If the rod can the rod be twisted back into alignment I guess the big end has gone. How does the barrel look?

please keep us posted.

Cheers,

Kamel.

[Long_Road]

I have removed the front cylinder, which has survived. I roughly measured the side play on the conrods: the front 1.5mm and the rear 4.5mm!

Perhaps this bike in it's previous life was poorly maintained and moved on when it gave up. For the record when I bought it there was also some electrical damage, sorted by NLM.

The conrods are fitted with the big end bosses facing. They don't feel stiff, but yes I was able to stand the rear one up so not entirely free either. Looking carefully at the alignment with the crank web the small end is parallel, and not free enough to twist. The cylinder studs as standard are located clockwise about 10 degrees from straight. The front small end is also aligned to the crank webs. Surely the conrod's small ends should be parallel to the crank rather than the rotated studs? In less words, the photo makes the small end look like it has been twisted clockwise, but it isn't. Play is only side-to-side.

Another gruesome photo:

IMG_0082.JPG (46.61 KiB) Viewed 5842 times

Kamel don't feel guilty. You helped save this poor bike before things got worse.

I'm confident the conrods are shot. I expect the crank journals to be damaged/worn out too. I have a wrecked piston and a cylinder that needs re-sleeving/replacing and boring out to 375cc. What I don't know is what else could be wearing or already is worn out, judging by what has already been found. Fortunately prior to undertaking this project/nightmare I sold a motorcycle to fund it - a Honda 400-4.

I think I'm going to have a chat with Lusso Veloce. I like the challenge of undertaking this myself, and as we know riding a bike which you fixed yourself is that much more fulfilling. However I believe there are certain engineering and machine shop procedures such as tolerance and alignment measurements which I couldn't do. This could lead to even more problems down the road.

[MickeyMoto]

Have a chat with SEP at Kegworth. They did my crank. Take the barrel, they can make new liners.

[Ian_C]

Having read back over this thread and three failures related to the rear cylinder I would check that the bore of the rear cylinder barrel is square with the barrel flange face that mates to the crankcase.
If the re-linering and cylinder boring is not carried out correctly by referencing the operation to the bottom flange face of the barrel, particularly in the direction of the crankshaft axis, then the piston is forced to operate with an un-intended side load. This could explain any wear found on the side faces of the big end and would load up the gudgeon pin too.
Worth checking out I feel, unfortunately I live a little too far away from you to measure this all out for you in my machine shop.
Ian

[mbmm350s]

Hi
The side play is measured at the crank end of the rods by a feeler gauge between the two conrods. It would be very amplified at the small end. Unfortunately if the side play is excessive the replacement rods would be needed.
Ian C makes a good point about the barells being bored perpendicular I had a recurring seizure on one side of an A7SS until this fault was found.
Mark

[Long_Road]

Thank you Ian and Mark, that could well be the cause of the problem all along. Whoever ends up with the pleasure of carrying out the repairs I will ask to measure the squareness. The 375 rebore was carried out by a company NLM used but it's possible the standard bore was also out of alignment, and they just went with that.

I just measured the side play at the crank ends of the conrods and it is within tolerance, however the rear conrod has considerably more of a side-to-side rock than the front, possibly as a result of this side load.

The rear piston lost it's gudgeon pin clip because the groove it sat in actually melted away. Incredible. I can see the other side has partially melted too. It's possible the gudgeon pin and small end were getting really hot.

[72degrees]

If all else fails I have a spare pair of cylinders that evguru sold me. I had intended to use them on the Forgotten Error but in the end stuck with the ones that came with the engine I rebuilt. Can't remember what oversize they are, but surely can go to '375'. PJ Motorcycle engineering ion Wednesfield did the boring (to +.6) for the FE. They seem to know what they are doing. Can't see me needing two spare sets (the FE is now effectively a rolling spares kit )

[72degrees]

What I don't know is what else could be wearing or already is worn out, judging by what has already been found..

In my experience, with the 77 Strada lump rebuild - gearbox bushes. I wish now I had searched harder, possibly contacting Italian dealers, or looked in to getting some made. The place that made a custom small end for my Gilera 98 might be able to using the old ones as patterns. A couple of them were really badly worn.

Otherwise, valve guides - I think NLM had a batch made before Mdina took over ?

I might eventually do a re-re build and also replace the mystery cam with something closer to an L5 - what's the latest state of play on those
semi-mythical beasts ?

[Long_Road]

Pete your generosity knows no bounds! I don't want to deplete your spares supply.

On that one test ride I noticed how good the gear selection was - better than the Japanese contemporaries in the garage, so I think that the gearbox has got away with it. I do have to find neutral with my hand, but I put that down to typical Italian 'character'.

I agree an L5 cam would be nice, but I'm not thinking that far ahead yet. An engine that actually works first would be great.

[harrymuffin]

ou have had a lot of problems with your engine and I have resisted from offering suggestions apart from checking the ‘gate’ slides of you carbs. If the engine is assembled correctly then you should not have had the problems that you have now uncovered. I have built a few moroni engines 350’s 374’s 500’s and my last a 5speed bottom end with a 507 top end grafted on, a number of these engines from other owners with one or two engines ‘wrecked’. I currently have a very early 350 belonging to another member that is having the bottom end rebuilt with new bearings throughout plus crank regrind and new gudgeon bushes.
The reason I have posted and although of what i have said above do not regard myself in anyway an expert, as new problems come along not seen before, but expand our knowledge hence the saying ’better to be a scholar than a master’. So, whilst dosing today after lunch and meditating, your problems came to mind which no none has as yet mentioned and that is the orientation of the the conrods. As you know the cylinders are off set from the centreline of the engine, to the left and to the right in order to accommodate the two conrods on one crankpin. The conrods therefore have to be offset from the perpendicular axis of the gudgeon pin and conrod centre line, but the conrods for each cylinder are the same for cheapness and expediency. It maybe just that the person who assembled this engine assumed that the conrods offset when fitting to the crank pin should be the same OR inadvertently fitted them the same such that the rear conrod does not have the correct offset and so is not correctly aligned in the cylinder across the engine and consequently forced itself to push the pin through the piston and out the side because everything is out of alignment. My question is therefore, are the offsets off the conrods the same? You can check this if the engine is still assemble by rotating the crank to front pot. If you can PM me with a contact address I can send you some snaps of the assembled crank that should clarify things.
If you intend to rebuild the engine yourself and they are not difficult to do and you really need any special tools, I do have a full set of ‘special’ tools if you should need to borrow them as I hope to have this engine back together over the xmas period.

[Long_Road]

Thanks for the photo harrymuffin - it helped me understand what you meant. After a long look at said photo, I saw that the rods are both facing the same direction, in other words the L/H or rear rod the wrong way round, which would lead to the same problem my engine has.

I have just had a good look at my crank through the cylinder openings and the rods are both fitted correctly, the wider part of the big ends facing each other. However it also looks (I only did this by eye) that the rear small end is not central in the cylinder opening - it sits to the left, which corresponds to the small end bush sticking out the right, and the cylinder damage occurring on the left side of the bore. It looks like I have a bent conrod.

How is another matter. Maybe some more photos are in order.

[harrymuffin]

I am glad that the photos have helped in the identification of your problem, but to confirm without takeing apart just yet though a rebuild sounds in order, do as I suggested in my email to you by confirming the little end is out of kilter. The bush is 17mm and the bore of the gudgeon pin is usually 12mm sofind a rod or wooden dowl thet is a comfortable fit in the bush about 4-6" long insert and then rotae the crank and see if one side touches the crankcase before the other. Idealy a matal rod through the centre of the pin would be better and you could use a 12mm drill to get a more accurate deduction. Having done that the bush should be in the centre of the little end, sticking out equally both sides, the hole in the top of the little end is in the middle of the width of the little end lined up with the forgeing flash mark 7..5mm either side. Lower the rod to it's most bottom and lay a rule or straight edge along the crankcase joint and you should then be able to double check the rod is where it should be in the middle, with a rod through the little end you will be able to determine if the rod is twisted or bent.
If as you have sugested this problem was there before you bought the bike, then the previous owner nust have had a catastrophic, most likely, failure of the piston which is a known problem with these engine. A crack propogates from the expansion slit and hole to the bottom of the skirt and if not identified the bottom break off and hopefully just ends up in the sump but if it flyes around can cause the piston to break up and with the crank still going round the conrod will flail around and do itself a mischief, bend maybe not very much but enough when refitted to cause the problems you have had.
On the bright side bent conrods were common place and would be straightened as normal practice in engine remanufacturers, unfortunately we live in a throw away society now and the skills are becoming rarer to find. As I suggested you should be able to find a firm in the Southampton area by virtue of the ships needing maintenance find one that would have the ability to sort the rod out and carry out what I suggested regarding machining and salvage. If you feel the need or advice from firms suggests another rod you will have to match to the one you have as they would be fitted as a pair weight wise. You already have my suggestions regarding recovery of the barrel.