Dondolino Pistons and valve collet holder

[Bill Irwin]

Hi all

I'm progressing slowly with rebuilding my Dondolino replica engine.  The engine is fundamentally sound but everything I look at seems to need attention.  With the engine together and valves timed I have had to machine pockets in the new Falcone Sport piston to clear the valves.  While doing so I noticed a hairline crack in the crown where the exhaust valve had hit it (the original reason for pulling the engine apart to check everything).  Closer inspection has revealed another crack at right angles on the underside.  I could have it welded but I'd rather replace it with the correct Dondolino piston.  I need 88,6 but have only been offered 88,5 or 89 at 200 euros (by kingofpistoni) or alternatively a set of 4 at 148 euros each (by cps).  Does anyone know of another source or alternatively is anyone interested in sharing the cost of a set of 4?

I'm also looking for an upper valve spring holder and collets.  I assume that these are the M8010 as used on the superalce.  One of them has been made out of thicker alloy on my bike and is fouling the spring lower legs at full lift.

The problem I had with the upside down gear change has disappeared with correct assembly.  Now I can't for the life of me understand how it was possible to assemble it in such a way that the change was reversed.

As a newbie to Guzzi singles I'd like to record my appreciation for the help and advice given to me by members of this group – especially Patrick, Jerry, Antonio and Gordon.  With their help I have really enjoyed getting to understand these wonderful old engines.  The soundness and ingenuity of Carlo's original design constantly surprises and delights me.

Cheers Bill

[Gordon de la Mare]

Bill

With reference to valve spring holder and collets I guess that we are down to how much of a replica is it?

The original Dondolino exhaust valve was sodium filled and the top of the stem where the collets fit is much larger diameter than the diameter of the valve stem itself.

The guides were split and had to be tapped out of the head to get the exhaust valve out.

If not this type then I think that you may need to do some measurements on the stem, the cap, etc, so that these can be compared to other models to see what fits and hope that another list member has those parts on hand to do a comparison.

Sorry for lack of complete help here.

Cheers

Gordon

---

From: Bill Irwin <bi...@irwin.gen.nz>
To: "guzzi-...@googlegroups.com" <guzzi-...@googlegroups.com>
Sent: Monday, 9 July 2012, 8:51
Subject: [guzzi-singles] Dondolino Pistons and valve collet holder

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[Bill]

Hi Gordon

My inlet guide is split and the stem is a straight 8mm in diameter with a 10mm top.  The exhaust guide (and valve) is 10mm and not split and the valve is waisted to take 8mm collets.

Cheers Bill

On Monday, 9 July 2012 20:57:21 UTC+12, Gordon de la Mare wrote:

Bill

With reference to valve spring holder and collets I guess that we are down to how much of a replica is it?

The original Dondolino exhaust valve was sodium filled and the top of the stem where the collets fit is much larger diameter than the diameter of the valve stem itself.

The guides were split and had to be tapped out of the head to get the exhaust valve out.

If not this type then I think that you may need to do some measurements on the stem, the cap, etc, so that these can be compared to other models to see what fits and hope that another list member has those parts on hand to do a comparison.

Sorry for lack of complete help here.

Cheers

Gordon

---

From: Bill Irwin <bi...@irwin.gen.nz>

To: "guzzi-singles@googlegroups.com" <guzzi-singles@googlegroups.com>

Sent: Monday, 9 July 2012, 8:51
Subject: [guzzi-singles] Dondolino Pistons and valve collet holder

Hi all

I'm progressing slowly with rebuilding my Dondolino replica engine.  The engine is fundamentally sound but everything I look at seems to need attention.  With the engine together and valves timed I have had to machine pockets in the new Falcone Sport piston to clear the valves.  While doing so I noticed a hairline crack in the crown where the exhaust valve had hit it (the original reason for pulling the engine apart to check everything).  Closer inspection has revealed another crack at right angles on the underside.  I could have it welded but I'd rather replace it with the correct Dondolino piston.  I need 88,6 but have only been offered 88,5 or 89 at 200 euros (by kingofpistoni) or alternatively a set of 4 at 148 euros each (by cps).  Does anyone know of another source or alternatively is anyone interested in sharing the cost of a set of 4?

I'm also looking for an upper valve spring holder and collets.  I assume that these are the M8010 as used on the superalce.  One of them has been made out of thicker alloy on my bike and is fouling the spring lower legs at full lift.

The problem I had with the upside down gear change has disappeared with correct assembly.  Now I can't for the life of me understand how it was possible to assemble it in such a way that the change was reversed.

As a newbie to Guzzi singles I'd like to record my appreciation for the help and advice given to me by members of this group – especially Patrick, Jerry, Antonio and Gordon.  With their help I have really enjoyed getting to understand these wonderful old engines.  The soundness and ingenuity of Carlo's original design constantly surprises and delights me.

Cheers Bill

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[David Roper]

Bill, my Dondolino was the same with the split intake guide with a 8mm stem (but 10mm top) and a one piece exhaust guide with a 10mm sodium filled valve.  I assumed the exhaust had been retro fitted.  According to the museum, my bike was actually built as a Condor in June of '39.  At some point it was uprated to Dondo specs. with cam, carb, and brakes. I've had valves and guides made for it--Black Diamond, 8mm stems. The original piston had cut aways for valve clearance.  I had JE make me pistons, 89mm with a higher dome for more compression.  I'm running about 9:1 now.  I justified having the four made because I want to build a second motor for a later style bike ( sort of a hybrid '55 works single and Ken Sprayson/Arthur Wheeler frame), and figured having a spare piston for each motor on the shelf wouldn't be a bad thing. I plan to race the Dondolino next at Mid-Ohio 21-22 July. Dave Roper --- On Mon, 7/9/12, Bill <bi...@irwin.gen.nz> wrote:

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[Dino]

Dave

I hope to see you there.  I am taking the Airone and SuperAlce down to ride around on. 

Dino

On Jul 9, 2012, at 11:00, David Roper <rave...@yahoo.com> wrote:

:

[Bill Irwin]

Hi Dave

Do you have a spec sheet reference for your J&E piston?  I'll ask them for a price too.  It looked like a days work to fill in their order form so a reference to what they made for you should help. 

I don't know if my valves are original dondolino or not. My whole bike is a bit of a mystery as it seems to be a real mix. The cases are definitely not magnesium and the primary gears are not straight cut. I can't find any frame number but it looks old and well used and is identical to photos of genuine bikes I have studied. The carb and cams are original Dondolino. The tank is steel rather than the alloy used for replicas and was full of sludge.  The poor workmanship everywhere doesn't indicate construction of a replica rather very amateur efforts to keep an old bike going on a budget. I'd love to know its history. 

Good luck at Ohio.  I don't have the balls for racing and I couldn't live with the blow ups. I love watching others do it though. 

Cheers Bill

[Miles Carnahan]

Bill,

I have the spec sheet for J & E that Jerry used to get pistons for his Donolino. I'll be home later and scan it for you.

Sent from my iPhone

[David Roper]

Bill, the JE invoice # is 1003461 The order # is 857432 Product I.D. is 311318 I had to pay a $75 'piston sample layout'; if you don't, keep me in mind. My frame # is right under the seat.  My tank(s) is (are) steel, but much of the frame is aluminum.  What about your wheels? DR --- On Mon, 7/9/12, Bill Irwin <bi...@irwin.gen.nz> wrote:

[Bill Irwin]

Thanks Dave

I have found another Italian maker www.motorpiston.it who can supply a single forged piston in the diameter I need so I'll go that way rather than buying 4.

My subframe, guards and rims are aluminium and hubs are magnesium.  The wheels look like they have been rebuilt with new black spokes.

I'll have a closer look under the seat.  I had been looking around the steering head.

Cheers Bill

[David Roper]

Let us know how you make out with www.motorpiston.it.  That could be a  good contact.

[Bill]

I have ended up buying a forged 89mm piston from www.kingofpiston.com for 250 euros including shipping.  He was easy to deal with but is not registered for IVA so he couldn't deduct it from my order.  despite that he was cheaper than the others who mostly wanted to sell me a minimum of four pistons.

Thanks to Antonio I discovered that my bike was supposed to have alloy valve collets and keepers so I have machined up some new ones out of high tensile alloy.  I'm fitting a K-Line insert to the exhaust guide.  the valves and the inlet guide were within spec.  Just waiting for the piston to have the cylinder bored and then I should be able to fire it up.

Cheers Bill