Author Topic: 850 big bore kit  (Read 477 times)

Offline ray bear

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850 big bore kit
« on: December 04, 2021, 08:50:00 PM »


Hi all, Have a set of 950 Gilardoni barrels that have had the skirts machined down to fit my 850 Eldo crankcase, is there any reports about issues regarding the skirts breaking due to machining away some of there strength  My eldo has had some gudgeon rattle for the last 70,000 kilometers and I purchased them many years ago because of the rattle  but have allways worried that they may be fragile so have just put it off and  kept riding but I just think its time to stop the rattle  and would like any nerve settling feedback .  I have the lightened Wiseco  gudgeons to install so hopefully balance wont be too much of an issue ,   
PS: I think Charlie s had some experience in this matter. Thanks Ray
« Last Edit: December 04, 2021, 08:59:24 PM by ray bear »
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Online Antietam Classic Cycle

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Re: 850 big bore kit
« Reply #1 on: December 04, 2021, 09:06:58 PM »
Never heard of any issues, the "skirts" are still plenty thick (assuming the minimum amount necessary was removed).
Charlie

Online PeteS

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Re: 850 big bore kit
« Reply #2 on: December 04, 2021, 09:23:31 PM »
I was told by Manfred the crankcase gets bored out, not the skirts reduced. Thats how I fitted mine.

Pete

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Re: 850 big bore kit
« Reply #3 on: December 04, 2021, 09:44:30 PM »
I was told by Manfred the crankcase gets bored out, not the skirts reduced. Thats how I fitted mine.

Pete

Both ways get the job done. Boring the case is preferable if the engine is completely disassembled, if not then skirt o.d. reduction. Only around 1 mm is removed from the skirts, so it's hardly enough to compromise strength.
Charlie

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Re: 850 big bore kit
« Reply #3 on: December 04, 2021, 09:44:30 PM »

Offline ray bear

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Re: 850 big bore kit
« Reply #4 on: December 05, 2021, 02:41:54 AM »
Thanks Charlie, built up my confidence , unchartered territory is always a worry. Ray
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Online mtiberio

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Re: 850 big bore kit
« Reply #5 on: December 05, 2021, 06:13:29 AM »
you sure its wrist pin rattle and not the timing chain?
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Offline moto-uno

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Re: 850 big bore kit
« Reply #6 on: December 05, 2021, 01:49:47 PM »
 Not too sure how you've determined that the noise is gudgeon pin related , but try to verify when it's apart that
the pin fit in the rod top end is correct also . Peter
  Agree with chain tension check , and replace it with spring loaded unit.

Offline ray bear

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Re: 850 big bore kit
« Reply #7 on: December 05, 2021, 02:05:34 PM »
Theres no chain its gear drive, has cast bores but I dont know anything about its past history as its never been apart in the 70,000 ks that I have ridden it, may even be a little piston slap but Im not interested so long as is stays together until I fit the new Gilardoni kits.I have been keeping the timing a little retarded and it keeps it quieter. Ray
72 V7 sport
73 Eldo police special
68 BSA rocket 3
74 Norton Commando
78 Honda CBX 1000
47 HRD vincent Rapide
XT 500 Yamaha
76 Convert
84 FLHX limited edition electra glide

Offline moto-uno

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Re: 850 big bore kit
« Reply #8 on: December 05, 2021, 03:56:46 PM »
  I should have looked closer at the pic , belt cover would have given it away . :thumb: . Peter

Offline henwilv

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Re: 850 big bore kit
« Reply #9 on: December 05, 2021, 05:51:13 PM »
Stein-Diese in Germany sells 949 kit like that for the 850s, nigusil barrels - can't see why you should have any problems
« Last Edit: December 05, 2021, 08:21:38 PM by henwilv »

LesP

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Re: 850 big bore kit
« Reply #10 on: December 05, 2021, 06:14:30 PM »
  I should have looked closer at the pic , belt cover would have given it away . :thumb: . Peter

If it is a 1972 it would have gears, the 4LS brake an add on ?
I think my March 1973 stamped Eldorado by engine number 058896 was just in as far as a chain drive.

I elected to bore the (1973) engine cases and add 177 grams of Mallory metal (1/2" and 5/*" for dynamic) to the crankshaft with the pistons being some 30 grams heavier than the factory 850 items.
I was not aware of the lighter piston pins at the time but imho you would get some form of added vibration as is with those heavy Gilardoni 948 slugs.

I believe Gilardoni enlarged the pushrod tunnels so the factory pre 948 non offset rockers work with no problem

Online PeteS

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Re: 850 big bore kit
« Reply #11 on: December 05, 2021, 07:39:03 PM »
There must be different types of pistons sold with these kits. The 992 kit for my round fin 850 LeMans were actually lighter than stock. They are slipper type pistons(short skirt) and came with the light wrist pins. You need to compare pistons before rebalancing the crank.

Pete

Offline ray bear

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Re: 850 big bore kit
« Reply #12 on: December 05, 2021, 08:34:17 PM »
very interesting feedback thanks guys, I will be getting crank balanced as I dont think the lighter pins will be enough, but I seem to recall one of Charlies posts where he mentioned it may be enough but will weigh it up when the time comes and Les p your correct the 4LS is an add on by me and engine # is 057309   Ray
72 V7 sport
73 Eldo police special
68 BSA rocket 3
74 Norton Commando
78 Honda CBX 1000
47 HRD vincent Rapide
XT 500 Yamaha
76 Convert
84 FLHX limited edition electra glide


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Harper's Moto Guzzi : Go Ride , Break Parts, Call me!
Harper's Moto Guzzi. Where we still answer the phone, use the highest quality parts, and also do Transmission, rear drive, and carb rebuilds fast. Call us at 816.697.3411 and get your problems resolved.
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