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Discussion in 'Old's Cool' started by fadingfastsd, Nov 7, 2014.
Just pull the whole thing outta the frame.
You are already in deep....
So this morning I took the left side intact piston and cylinder by VEEparts in El Cajon. They are a local Volkswagen parts house, and have some great guys working there. I had one of the guys measure the piston (83mm OD). I was hoping they would be able to compare the measurements to VW pistons and find one that I've heard so much about guys running in these bikes. He said it was the same size as a somewhat common piston for overbored VW's, but the stroke is probably wrong. Since they are not super common, they also can't be ordered in singles, only as a set of 4. He didn't stock them, and called around a couple other local shops, which didn't either. So not much luck here.
I'm going to keep doing research on using VW pistons on this bike, but who knows if that will ever work out. I did talk to Moto Guzzi Classics, and they have their full top end kit (pistons, cylinders, gaskets, rings, etc for both sides) in stock for $1200. That seems to be the smartest way to go, but I just can't drop that kind of coin right now. Going to keep trying to find a cheaper option to keep the bike on the road, even if it only gets me another year or two. Eventually I want to do a complete tear down on this thing and do my own custom build, so until then I'm really just concerned with keeping it on the road reliably and affordably.
IMHO, that engine is telling you what happed. I find when I have something like that in my garage, the bike is talking and it's up to me to listen, if you know what I mean.
I'd look at the reasons for holing a piston: running lean, running hot, timing. To me it looks like the left piston was pinging as well. Is the piston crown rough like it's been media blasted? Also there is a lack of carbon on the left piston. Maybe that means it was pinging as well. If that's the case, I'd wanna find the cause.
One thing to add about the timing is look in Guzziology. I know for my tonti framed bike I set the dual points statically so they both fire at the TDC mark, then start the bike and set one cylinder to full advance, make sure it's at full advance on the other one. Once I do this, my timing marks are off at idle, but it runs great. According to Guzziology, it not unusual for the idle timing marks to be off and it's best to set it for full advance. I don't know if there's a trick like this for the loop frames, but that might be worth looking into.
Also, do you have an intake lead or carbs that are too lean. Look at your plugs as an indication, but put that infl together with how it's run over the last 600 miles: does it transition onto the needle or mains smoothly, does it run well on the needle and main jets? I know with some British bikes we play with, sometimes the intakes warp and we have to lap them flat, especially with Amal concentrics. I've seen one set of Dell Ortos a little warped, but no leak. I'd check all the mating surfaces on the carbs, intakes and head. Also check you air filter and air box set and make sure it's not leaking. Lastly, check your plug's heat range. In my exprience, you have to be way off to cause problems, but worth checking.
Good luck with it. IMHO, I'd pull it down to the block, clean it out, spec the crank, bearings, put new pistons in, balance the lower end and replace whatever needs replacing. That way you'd know your good, but that's easy to say sitting behind a computer. Get her back on the road. She a gorgous bike.
On a loop frame you can only check one cylinder, the other could still be off.
What you said. I think there's going to be a wave of people who jump on old bikes and dont' know the warning signs.
Possible that a jet got clogged by old fuel and it leaned quickly, but I've also seen points widen when loose and that advances timing. I know they're supposed to close, but that set didn't read the instructions.
This is why I wrote this...http://carl.krall.org/wordpress/motorcycle/ignition-timing-by-ear/
I don't want to seem ungrateful at all for the advice/ideas here, because I do appreciate the help. However, I'm getting a little tired of the implications that I didn't know what I was doing and ran this bike into the ground or something.
After I bought the bike, I fully tuned it up. The carb jetting was probably not perfect, but was close. The timing was set per the service manual. I had over 600 miles on the bike in this condition with no trouble. I had rode over 50 miles the night before the piston blew, with no issues whatsoever.
What I'm getting it, is there were no warning signs, and I didn't neglect the bike. I certainly didn't just jump on it and ride it into the ground.
Now if you guys read my previous posts, I'm trying to get the bike back on the road as cheap as possible for the next year or so. In a couple years I will do a full restoration/build on it. I can't put the money into it for a complete cylinder/piston kit, so even if it is short sighted and I have to rebuild the top end again in a year, it will serve my short term goals.
I've read online in many places about using VW pistons in this bike, but have not been able to track down which ones to use. That is my current goal.
I'm sorry if I implied that you don't know what you're doing. Wasn't meant that way.
It is your thread, but when it's public other people will read it for information, I was thinking more of that reader than you, since you are obviously capable. Planning to adapt a different piston made that obvious.
But at the same time: what caused the damage? That hasn't been answered yet and doing so would halt the well-meant suggestions about cause.
Don't know what you're doing? NO! NO! NO! I don't think you "did" anything wrong. However the bike is telling you something went wrong...very wrong.
My experience is coming from playing with several very old, classic bikes in the last 3-4 years. Some are mine, some aren't. Most are British and range in age from 1951 to my 88 airhead. It's the newest member of the crowd. The bikes range from Vincents, to BSA's, to Nortons, to bevel head Ducati's, etc. It's be a great experience to work on them as well as ride them. It's also taught me that sometimes things go pear shaped in a hurry. Sometimes things wear out. Sometimes they warp. Sometimes the clearances were too much and sometime too little. In all these cases, you want to find out why it went wrong to make the bike more reliable. Again, you may have done everything right and something still went wrong: no fault of your's.
In your case, I'd want to investigate further into why it swallowed a piston. Did you suddenly develop an intake leak? If so, where and why? Is there a nack for setting the timing (this is why I brought up Guzziology)? Is there something else going on?
My point was to brainstorm ideas while saying you've got a great bike. If there's a group of Guzzi riders in your area, maybe they have someone who could look at the bike and help. I know getting it running on a budget is one of your goals, but my experience with old bikes is that your guzzi is telling you it needs to be torn down and checked. In the engines that we've seen eat a piston, we always found bits of trash in oil ways, sludge traps, sumps, whatever. It may be easier to pull it all the way down now. Then you can spec everything out, renew seals and you'll know it's right. We seen a few a around here put back on the road by fixing the obvious stuff, and some seem to do OK. We've also seen some that have to be pulled apart again....just something to think about.
Good advice photomd. Pistons don't get old and develop holes - that's not a normal failure mode.
Like you said, something caused it.
Wouldn't be much fun to install a new set of pistons and barrels only to have a repeat.
Best to play Sherlock Holmes and figure out root cause - and you've got a whole crew here just waiting to help you out.
Now drop the touchy attitude and let's figure out what went wrong.
This is what I was referring to, when I recommended that you check your sludge trap. See the threaded hole just above the crankshaft? Centrifugal force pushes all the normal dirt and stuff that is in your oil and "filters" it by trapping it in that hole behind the plug. That oil is what lubricates your connecting rod bearings and everything else. If that hole is full, you will roast your bearings. Guzzi recommends the sludge trap be cleaned every 30,000 miles.
How many miles on the bike?
In your case, you have experienced catastrophic engine failure. The pieces of the melted piston should have ended up in the sludge trap, and hopefully not on your main bearings. There is only one way to find out...
Pull it all apart and take a look.
Holy cow have the prices of Gilardoni cylinders and pistons come down. Here's the link to what you need. Call MG Cycle and see when they are ordering more and when they'll be in. When I bought mine 6-7 years ago, it was roughly 2x that price. IIRC, they place an order yearly and you 'll probably have it by Feb. When I rebuilt my Guzzi, I also had the bottom end dynamically balanced. It's butter smooth from 3500-5000 rpm. It only cost around $40 and it's smoother than before I pulled it apart. Anyway...good luck. We're all interested in what you find.
From what I've been told by several reliable sources, the next batch of Gilardonis aren't expected until May 2015 maybe. Not a sure thing at this point, they might decide to not make any again next year (just like they did this year).
How much is your time worth? Mine is pretty valuable to me, so searching out a VW piston that might work okay after modification just isn't worth the trouble to me. You don't get much cheaper or easier than buying a set of good used Convert/G5/SP iron liner cylinders and pistons. There's a set on eBay even cheaper than the ones I posted before:
Any good machine shop can turn down the spigots so they'll fit into the Eldo case, then they're a bolt on deal.
Another idea is to find a complete Convert/G5/SP engine. I found one for $150 a few years back, changed the timing cover, bought a crank adapter from Mark @ Moto Guzzi Classics, drilled and tapped holes for the generator mount on the top of the crankcase and it slotted right into the Ambassador that I was building at the time. Doing the same thing again, but this time with a $200 California II engine.
That price, $384 is for one cyl/piston. Seems roughly the same as it was two years ago to me.
Really? What a shame. I'm very happy with mine. My engine was puking oil when I bought it. The piston to bore clearance was too large so I put in a set of Gilardonis. They mearsured out perfectly and I've now got an engine that oil tight, smooth and runs great.
huh....you're correct...maybe I should read a little more closely before posting.
Been super busy the last couple days, sorry for the delay with an update. No worries, I'm sure I misread what you meant. I'm annoyed with this whole situation and shouldn't have been so touchy in the first place. Sorry for the being a jerk.
I'll post updates below.
I did talk to MGCycle last week. They MIGHT have Gilardonis in stock in Mid December, but no guarantees. He said it could easily get pushed til next year.
The only option for parts currently in stock that I can find is from Moto Guzzi Classics here in CA. They have their complete kit (pistons/cylinders/rings/gaskets, etc) in stock for $1200. Still trying to find a cheaper option for now.
I dropped the oil pan last Thursday. I siphoned off the oil, and got down to the bottom of the pan. There are chunks of piston everywhere. There are some small metallic flakes in the oil as well.
I had the screen on the oil pickup, I'm hoping that kept it from puling too many metal shavings into the motor. I will be pulling that apart tomorrow to check it out.
On a side note, I removed the generator to have more room to work, and found out the generator mounting bracket is cracked in half as well, so I've got that going for me
Probably a stupid question, but I assume I need to remove the crank completely to access this sludge trap correct? Thanks for the heads up on this.
I may end up going this route. I didn't realize I could get a good set of pistons/cylinders for a couple hundred bucks. What do you mean by 'turn down the spigots'?
By "turn down the spigots" I mean machine the bottom of the sleeves where they protrude into the engine case to a smaller diameter so they'll fit. They might fit as-is, but there might not be enough clearance to allow for expansion.
You might need Tonti rockers and/or to open up the pushrod tunnels in order for the pushrods to have adequate operating clearance.