Author Topic: cx100 base gsket and cyl height  (Read 1493 times)

Online ital4me

  • New Egg
  • *
  • *
  • *
  • Posts: 56
cx100 base gsket and cyl height
« on: January 17, 2023, 09:43:30 AM »
Okay I have a strange one for you folks. I am in the process of replacing the head gaskets on my CX100. After removing the heads I found that at TDC piston on the right side is lower in the barrel then the left. Approximately .040 difference. Fearing the worst I did started an investigation. I removed the barrels and could not detect any play in the rod journals. The right piston was approximately .040 higher then the left side which at BDC is flush with the case. I measured the stroke albeit hard with the barrels off. Because of this I measured 6 times and took the average reading. The stroke was the same. Ok, If you have stayed with me so far there are two mysteries to solve. Why is the right side piston +.040 at BDC? Given that the stroke is the same and it starts out higher at BDC then why is the top of the piston lower at TDC than the right? I have done the measurements twice yesterday and the same results. I am going down to take them again. The bike is a former race bike and is not stock. It has Norris cam in it. I realize that I am an older codger but I think I have most of my marbles. Any ideas?

Offline Tom H

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 3377
  • Location: So. Cal.
Re: cx100 base gsket and cyl height
« Reply #1 on: January 17, 2023, 09:53:09 AM »
Different piston height from wrist pin to crown? Different rod lengths? Is there a spacer under one cylinder or two base gaskets?

Hope this helps,
Tom
2004 Cali EV Touring
1972 Eldo
1970 Ambo V1000
1973 R75/5 SWB with Toaster
2007 HD Street Bob
1953 Triumph 6T (one day it will be on the road!)

Offline guzzisteve

  • Gaggle Hero
  • *****
  • *
  • Posts: 11424
  • "Just Ride It"
Re: cx100 base gsket and cyl height
« Reply #2 on: January 17, 2023, 10:27:22 AM »
You opened the can of worms. Sounds like one side was replaced when it let loose. I'd pull all parts involved, at least pistons.
"Pray through Carlo & your bike shall be healed"
Location: Planet Earth

Online acguzzi

  • Gosling
  • ***
  • Posts: 325
Re: cx100 base gsket and cyl height
« Reply #3 on: January 17, 2023, 10:42:32 AM »
if the stroke is the same then the piston higher at TDC has to also be higher at BDC if that is not what you see then I would suspect the measurements. This should not be affected by con rod length.

Wildguzzi.com

Re: cx100 base gsket and cyl height
« Reply #3 on: January 17, 2023, 10:42:32 AM »

Online MattP

  • Hatchling
  • **
  • *
  • Posts: 104
Re: cx100 base gsket and cyl height
« Reply #4 on: January 17, 2023, 11:51:35 AM »
Well  no 1 both clinders share the same crank jurnal  crankcase could have ben machined, cilender base,. difrent pin location in pistons dif cilender higth dif, rod lengths. I wonder how it ran like this would be hard to tune I would think.

Online ital4me

  • New Egg
  • *
  • *
  • *
  • Posts: 56
Re: cx100 base gsket and cyl height
« Reply #5 on: January 17, 2023, 01:59:35 PM »
Hey thanks for the replies. I just came up from double checking the measurements. The stroke is close enough and given my crude measurements .030 I will call it even. The pistons are both Labeled Guzzi ACA. Both sides had base gaskets .020 thick. It was running fine when put up about 5 years ago. I am in the process of recommissioning it. I could see some weepage  on the right side in the head gasket area. I ordered a gasket set and it should be here tomorrow. After noticing the different piston heights at TDC I decided to pull off the jugs imagining the worst. I noticed that the left piston is .020 from case to piston at BDC. On the right it's .050 and winds up lower than the left at TDC. The barrels measure the same every where. It does not make sense. I guess my plan is to put the left side together as normal. Then dry assemble the right and see where I am at. One more clue is the left side was burning nice. The right side is looking rich. This could mean be caused by a few things, possibly lower compression? I should be able to get better measurements with the barrels on. I will keep you informed when I have proved myself a fool.

Offline moto-uno

  • Gaggle Hero
  • *****
  • *
  • Posts: 1397
  • Location: Burnaby , B.C
Re: cx100 base gsket and cyl height
« Reply #6 on: January 17, 2023, 05:34:29 PM »
 I don't want to possibly state the obvious,BUT, have you measured the barrels ? (Head gskt surface to base gskt surface) Peter

Offline fotoguzzi

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 19931
  • vee git tooh soon oldt und too late wise -my Dad
Re: cx100 base gsket and cyl height
« Reply #7 on: January 17, 2023, 06:04:53 PM »
 :popcorn:
MINNEAPOLIS, MN

Online MattP

  • Hatchling
  • **
  • *
  • Posts: 104
Re: cx100 base gsket and cyl height
« Reply #8 on: January 18, 2023, 11:47:27 AM »
It is real simple, only 4 things that could change to cause this , different cyclinder highth different pin location in pistons different rod lengths different deck higth on crankcase. how are you mesering the crank throw do you have the rods out. if so put a wrist pin in both rods , and check same with pistons. You imply the pistons are the same, if so I would bet a case of diearea the rods are different. again , If one side crank tdc is higher then the same side bdc should be the same amount higher , this not what I think it is a fact. If this is the case, and all other parts are the same. then I would be surprised.

Offline John A

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 4905
  • No way to slow down...
  • Location: Hager city ,western WI
Re: cx100 base gsket and cyl height
« Reply #9 on: January 18, 2023, 11:54:16 AM »
A bent rod could do it.
John
MGNOC L-471
It is easier to fool people than it is to convince them that they have been fooled-Mark Twain
99 Bassa, sidecar
02 Stone
84 V65C
15 F3S Spyder

Online cliffrod

  • Gaggle Hero
  • *****
  • *
  • *
  • Posts: 2170
  • AC Button II
    • Carolina Sculpture Studio
  • Location: Spartanburg, SC USA
Re: cx100 base gsket and cyl height
« Reply #10 on: January 18, 2023, 01:24:09 PM »
Hey thanks for the replies. I just came up from double checking the measurements. The stroke is close enough and given my crude measurements .030 I will call it even. The pistons are both Labeled Guzzi ACA. Both sides had base gaskets .020 thick. It was running fine when put up about 5 years ago. I am in the process of recommissioning it. I could see some weepage  on the right side in the head gasket area. I ordered a gasket set and it should be here tomorrow. After noticing the different piston heights at TDC I decided to pull off the jugs imagining the worst. I noticed that the left piston is .020 from case to piston at BDC. On the right it's .050 and winds up lower than the left at TDC. The barrels measure the same every where. It does not make sense. I guess my plan is to put the left side together as normal. Then dry assemble the right and see where I am at. One more clue is the left side was burning nice. The right side is looking rich. This could mean be caused by a few things, possibly lower compression? I should be able to get better measurements with the barrels on. I will keep you informed when I have proved myself a fool.

So one side is both lower at tdc and higher at bdc than the other? 

Measuring stroke, You mention .030 and calling it close enough.  What does that mean? 

One side is .020 tall at bdc.  The other side is .050 tall at bdc, which is a difference of 030..  which is the same amount as the .030 you mention.  It’s also down at tdc.  That would indicate a difference in throw at the crankshaft journal, because one side is traveling up & down a shorter (or longer, depending upon which side is being measured) distance.  If that journal assembly is worn .030 on bottom and also worn on top, it would produce the condition you are experiencing.

A correctly phased out of round journal assembly can cause shorter travel like this. Wear at top and bottom of rotation (where stresses are greatest and wear is most likely) will push piston a shorter distance up the cylinder and pull it down less at bottom of stroke.  badly worn rod bearings- at middle of each bearing, on top and/or on bottom- can cause such deficient in travel.  Similarly worn pin bushing or a crankshaft journal can do the same thing.  But rod bearings are more sacrificial by design so likely to be the more heavily worn components. 

I agree with Steve. If one side may have been replaced while other side was left alone & now the left-alone side is not happy, I would expect what you’re seeing….

Keep up posted.

1973 V7 Sport  "Now THAT'S a motorcycle!"-  Master Sculptor Giuliano Cecchinelli
1967 V700 Corsa Record
1981 Lemans CX100
https://www.youtube.com/watch?v=ExX3YmQel_Q
http://carolinasculpturestudio.com/
Carolina Sculpture Studio YuoTube Channel-
https://www.youtube.com/channel/UCzSYaYdis55gE-vqifz

Online Moparnut72

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 2238
  • Location: Quincy California
Re: cx100 base gsket and cyl height
« Reply #11 on: January 18, 2023, 02:34:06 PM »
One possibility I am thinking of especially since this is a former race bike is that there was an issue with the crank. Maybe there was a problem and the shorter stroke side of the crank rod pin was damaged. Then it was welded up and was reground but at a shorter distance from center than stock. This it would be a little down at tdc and up at bdc. I think I am seeing this correctly. What else could it be?
kk
Mopar or Nocar
2023 V100 Marina
2019 V7lll Special
MGNOC #24053
Amiga computer shop owner: "Americans are great consumers but terrible shoppers".

Offline nc43bsa

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 1353
  • Location: Mooresville NC
Re: cx100 base gsket and cyl height
« Reply #12 on: January 18, 2023, 06:41:45 PM »
I might be missing something here, but I think what you are saying is the single crank throw on the CX has a different stroke for each of the connecting rods, right?
1990 MilleGT

Offline moto-uno

  • Gaggle Hero
  • *****
  • *
  • Posts: 1397
  • Location: Burnaby , B.C
Re: cx100 base gsket and cyl height
« Reply #13 on: January 18, 2023, 07:00:58 PM »
  Has "Ital4me" actually measured the barrels to see if one has been shaved, which would explain this discrepancy .
  If anyone has seen a guzzi crank from a Tonti you would know how near impossible it would be to have 2 different strokes .
  Hope he gets back to us soon .  Peter

Online Moparnut72

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 2238
  • Location: Quincy California
Re: cx100 base gsket and cyl height
« Reply #14 on: January 19, 2023, 08:57:02 AM »
I haven't so please forgive me. I am now as stumped as everyone. The way it was explained and as I understand the problem I don't see how the length of the barrel would be relevant.
kk
Mopar or Nocar
2023 V100 Marina
2019 V7lll Special
MGNOC #24053
Amiga computer shop owner: "Americans are great consumers but terrible shoppers".

Offline nc43bsa

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 1353
  • Location: Mooresville NC
Re: cx100 base gsket and cyl height
« Reply #15 on: January 19, 2023, 10:12:03 AM »
I have read through this thread three times and the only conclusion I can come to is that one or more of the following is true:

1) the L & R pistons are not the same

2) the L & R cylinders are not the same

3) the L & R connecting rods are not the same

I can see no way the strokes of the two cylinders could be different on a BB Guzzi without some REALLY fancy machine work, and I cannot think of any reason for doing it. 

I did hear of a racing Harley that had different strokes for the front and rear cylinders, but that was to increase displacement without detection by the race officials.  Those of us who know how a Harley is put together can visualize just how difficult that was to accomplish.
1990 MilleGT

Online MattP

  • Hatchling
  • **
  • *
  • Posts: 104
Re: cx100 base gsket and cyl height
« Reply #16 on: January 19, 2023, 03:00:09 PM »
correct I stated this twice already However as I said stated  pecked here ,there are 4 things the crankcase deck could have ben machined and or altterd nothing to do with the crank nothing to do with the crank nothing to do with the crank sheere foolishness. How ever honda did grind offset crank jurnals, but this not a the case. I dan,t know where this thing is if it were close I would have the answer with in 10 minutes For free of course.  probubly the one cyilnder was not set all way down on crankcase when you turned it over , would be my gess. ran fine tell I took er apart. I bought a fey bikes and cars that I was told ran good till they tuned them up. A trident 71 with the center piston burnt through . I could start that with one hand. Ran the bitch dame neer wide open from Bolixe ms to mlps mn and back.Sorry Oh I gess I did install a new piston first.

Online ital4me

  • New Egg
  • *
  • *
  • *
  • Posts: 56
Re: cx100 base gsket and cyl height
« Reply #17 on: January 19, 2023, 04:05:36 PM »
Hi, An update for you. I didn't get to cylinders today but I did do the measurements over 6 ways from Sunday. I am measuring from the deck of the block to the piston top using a dial caliper. The barrels are off at this point so holding the piston just right is not an exact science. This is what I measured today.

Left cylinder at BDC .025 at TDC 3.100 stroke 3.075
Right cylinder at BDC .075 at TDC 3.150 stroke 3.075

This is an average after many measurements and throwing out the top and bottom I have wiggled and pushed and pulled the pistons. The only play is side to side and no more than I would have expected. The cylinders are in great shape, no ridge and nothing odd. I have measured them in several ways. Overall height, skirt to mating surface and mating surface to top. They are the same. I suspect the rod length to be different.

The issue that started me down this road was noticing the right side piston being lower in the bore than the left side. Which still makes no sense. I suspect the answer tomorrow after putting the barrels back on. At this point I am feeling senile.

Online MattP

  • Hatchling
  • **
  • *
  • Posts: 104
Re: cx100 base gsket and cyl height
« Reply #18 on: January 19, 2023, 04:29:14 PM »
how can the right piston be lower in the bor when your measurememts indicate on bdc it is  and tdc  it is .050 higher any way how in the hell can  you or you measuring with flopy pistons and un suported and you can,t trust the timing marks to do this you using a diegre wheel. A few photos and you would be home, as for me I want to cry

Offline John A

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 4905
  • No way to slow down...
  • Location: Hager city ,western WI
Re: cx100 base gsket and cyl height
« Reply #19 on: January 19, 2023, 11:36:06 PM »
I’d be popping the rods out and checking them . If nothing else send them with the relevant measurements from the factory service manual to a competent engine machine shop for resizing the big end , straightening and rebushing the small end. Visually check /measure the crank pins for out of round, polish if necessary . Put a new set of bearing shells in and then you won’t worry about that part.
« Last Edit: January 21, 2023, 12:33:10 PM by John A »
John
MGNOC L-471
It is easier to fool people than it is to convince them that they have been fooled-Mark Twain
99 Bassa, sidecar
02 Stone
84 V65C
15 F3S Spyder

Online ital4me

  • New Egg
  • *
  • *
  • *
  • Posts: 56
Re: cx100 base gsket and cyl height
« Reply #20 on: January 20, 2023, 06:46:33 AM »
Matt, I agree my measurements with the barrels off is sketchy but I take measurements right over the wrist pin which reduces the error factor a bit. I have also taken them many times, thrown the obvious bad ones and averaged the rest. The measurement at BDC is the least error prone and at this point is of the most interest to me. Your comment about the timing marks is a good one. My method is to measure by feel which usually brings me to one tooth of in the timing mark. Then I just shift it to the mark. I agree it would be more accurate with a timing wheel but I don't think it would be off enough to change the .050 by much. I agree that none of this makes any sense as to the original issue that drove me down this road. The right piston being lower I hardly expected the piston to start the stroke higher than the left. I am looking forward to getting the barrels back on and see what it all looks like. The cylinders looked great. No ridges and the honing still visible. This bike was running fine when I put it up. After I pulled the heads for the new gaskets it was apparent that the right was burning rich. It always started and idled very well. All kinds of low end torque. Get it above 4 grand and hold on. Because it was running well I didn't do a compression check. Wish I had, it would have been more evidence. More to come. Oh, I am more at the scratching my head and questioning my sanity. The crying may still yet happen.

Offline moto-uno

  • Gaggle Hero
  • *****
  • *
  • Posts: 1397
  • Location: Burnaby , B.C
Re: cx100 base gsket and cyl height
« Reply #21 on: January 20, 2023, 10:14:44 AM »
  Good lord man , have you measured the barrels length from base gasket to head gskt surface yet and compared them ?  Peter

Online ital4me

  • New Egg
  • *
  • *
  • *
  • Posts: 56
Re: cx100 base gsket and cyl height
« Reply #22 on: January 20, 2023, 05:31:10 PM »
LOL, I hear ya. I did measure the barrels three ways total height, bottom of skirt to mating surface and top to mating surface. I can't detect any difference. I am convinced that the rods are different at this point. That doesn't explain the first issue. Like I said earlier I will know more this weekend and let you folks know.  No worries, I am prepared to look the fool. Been there before.

Offline jcctx

  • Gaggle Hero
  • *****
  • Posts: 1495
  • Location: Parker, Collin Cty., TX
Re: cx100 base gsket and cyl height
« Reply #23 on: January 21, 2023, 11:22:59 AM »
Maybe the block was not machined correctly?????????/

Online MattP

  • Hatchling
  • **
  • *
  • Posts: 104
Re: cx100 base gsket and cyl height
« Reply #24 on: January 21, 2023, 11:57:27 AM »
I stated that allready 3 times. how ever I for one would advise clean up gasket surfaces  reasemble new gaskets and orings ect. Gota take the pan off any way, 4 more bolts to pull the rods ect then he we will know what I suspect nothing is wrong, Remember it ran well before, Any way ladies and gentlemen take my advice grease your asses and slide on the ice. Sorry ben stuck in my brain for 65years

Offline moto-uno

  • Gaggle Hero
  • *****
  • *
  • Posts: 1397
  • Location: Burnaby , B.C
Re: cx100 base gsket and cyl height
« Reply #25 on: January 21, 2023, 06:24:01 PM »
  I feel a sh*t load better knowing you've eliminated that possibility  :bow: ! It, (shaving the base gskt surface) was a common practice a couple of decades ago
to get more go out of H-D Evos and all it cost was gaskets . Thanks for the follow up !  Peter

Offline John A

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 4905
  • No way to slow down...
  • Location: Hager city ,western WI
Re: cx100 base gsket and cyl height
« Reply #26 on: January 21, 2023, 07:23:25 PM »
There is no telling what parts might go on a race bike. It sounds like you got one with a good setup. It would be nice to go through it in the winter to make sure it’s up to snuff. Right now I spose the aim is to see what makes it different, fix that and put it back together with the least amount of messing around. It is curious though, I once bought a brand new 01 EV that had a bent rod from the factory. It died on its final test ride before I left with it. It had a visible bend you could see with the pan off.
I edited because I inadvertently wrote bent crank which would take some doing .I got a Bassa instead
« Last Edit: January 21, 2023, 08:14:09 PM by John A »
John
MGNOC L-471
It is easier to fool people than it is to convince them that they have been fooled-Mark Twain
99 Bassa, sidecar
02 Stone
84 V65C
15 F3S Spyder

Online ital4me

  • New Egg
  • *
  • *
  • *
  • Posts: 56
Re: cx100 base gsket and cyl height
« Reply #27 on: January 24, 2023, 07:17:10 AM »
Ok I have two follow ups. The first is I do have a rod that is .050 longer than the other. A head scratcher there. The issue that confused the crap out of me. The physical impossibility of the piston starting higher and finishing lower was caused by me entering the first measurement in the in the wrong column. I did mention the fool thing. I honed the cylinders and reassembled the engine. It has always been smooth and powerful. I am looking forward to a compression check to see how they compare, .050 is a significant difference in the squish band. I don't have the time or wherewithal to go further right now. Too many things going on this winter. I can't wait to find out more about the rod and fix it. See if there is a noticeable difference. I once replaced one piston to an overbore in a flat head V8 ford. I was a young man with two kids, no money and a patient wife. It was surprisingly smooth after. The engine and the marriage. The mystery of the longer rod will have to wait until later. Probably next winter. Thanks for the interest and ideas. Other than my being an idiot it was a fun mid winter process of discovery. Here is a pic of the head. Wanted to show you the ported heads and polished rockers. They had a couple of shims on the rocker shaft. I put the stock spring and washer back. The piston has teflon buttons in place of circlips.


Offline fotoguzzi

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 19931
  • vee git tooh soon oldt und too late wise -my Dad
Re: cx100 base gsket and cyl height
« Reply #28 on: January 24, 2023, 07:39:13 AM »
What is the benefit of polished rockers?
MINNEAPOLIS, MN

Online pressureangle

  • Gaggle Mentor
  • ****
  • *
  • *
  • *
  • *
  • *
  • Posts: 972
  • '97 1100 Sport i, '89 Mille GT
Re: cx100 base gsket and cyl height
« Reply #29 on: January 24, 2023, 07:43:19 AM »
What is the benefit of polished rockers?

Polishing removes surface imperfections, reducing the possibility of stress points fracturing. It was standard procedure at least into the 1960s when shot peening coupled with higher quality metallurgy made it unnecessary. It was also done after lightening rockers for increased RPM before alternative springs were easily available.

Do I see those intake manifolds held on with *WEDGES*? Outstanding!
Something wistful and amusing, yet poignant.

 

20 Ounce Stainless Steel Double Insulated Tumbler
Buy a quality tumbler and support the forum at the same time!
Better than a YETI! BPA and Lead free.
Advertise Here