Author Topic: I'm smoking on the right too!  (Read 2283 times)

Online muskrat

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Re: I'm smoking on the right too!
« Reply #45 on: 25.02. 2019 19:31 »
G'day Steve.
It could be a bent rod or just the little end bush not in square.
I'd be a little concerned about the big end shells using your method of straightening.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Online chaterlea25

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Re: I'm smoking on the right too!
« Reply #46 on: 25.02. 2019 19:58 »
Hi Steve,
There you ARE  *ex* I think you have found a (maybe not the?) problem
Before you go levering on the conrod, carefully check the small end bush for being bored /reamed off square
Get hold of a pair of engineering parallels and a length of 3/4in. ground steel bar (silver steel is ideal)
The 3/4in. rod should slide though the small ends, if they are in line then the rod should pass through both ( happy days)

Rod bend can be in two planes, inline with the crank and twist

Place the parallels front to back either side of the conrod, If the piston is machined square at the bottom  it should rest evenly on both sides
Cut 4 strips of paper and place these under each contact point between piston and parallel
hold the piston down onto the paper strips with a finger of one hand in the centre
use the other hand to gently pull on the strips, when all is good the pull should be even all round
If both loose on one side then bend to correct
A trickier situation is where the strips are loose diagonally, turn the crank over so the rod is opposite angle
and check again. If the loose strips change diagonal position then the small end is twisted
When you are confident the rods / small ends are good pass the 3/4in. rod though both the small ends, if they are in line then the rod should pass through both ( happy days)
If the pistons are cutaway on the bottom, you have to rely on the gudgeon pins sitting on the parallels

Then I had a memory flash back *eek*

Last year, I was asked to look at and solve a similar issue to your  bikes on an AJS 650 twin, But it smoked on both a bit and blew oil out the breather  *????*

All the above testing proved all good, bore to piston clearance was within tolerance and new rings had been fitted a year or so before but the problem remained  *conf*
I noticed side to side rub on the pistons, at the outside on the bottom and inside nearer the top??
I set up each cylinder on parallels on the mill and Mcgyvered  a DTI onto the side of a bar held in the spindle
Testing for "squareness"  by raising and lowering the mill table in front , back and side to side
I found that both bores were "Off square"  side to side to the base by 6/7 thou  *eek*

The owner has had the bike since the early sixties and never had it rebored in his ownership even thou it was +.020 ?
A very careful setup by my rebore guy got the cylinders true on +.040

I hope the BSA problem is in the small end bushes not in the cylinder for your sake

John

1961 Super Rocket
1963 RGS (ongoing)

Offline Swarfcut

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Re: I'm smoking on the right too!
« Reply #47 on: 25.02. 2019 20:10 »
Steve...A bent rod will produce a tell tale wear pattern on the piston skirt...check the old ones first.

   If you put a straight edge up the side on the thrust or back face of the piston you will find the land is slightly smaller above the top groove. So It is not unusual to look down and see the top ring, ask anyone who has worked on an old Ford Crossflow. Folks think this is bore wear. More important is the amount of sideways rock in the piston against the bore, the old time rule of thumb for estimating bore wear.

 Don't go bending alloy rods by eye unless as a last resort . Oh yes, we all assume those pistons have been drilled OK for the pins. You could turn it round, see if it leans the same way.

 Good stuff there from ChaterLea John.

 Swarfy.

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Re: I'm smoking on the right too!
« Reply #48 on: 26.02. 2019 02:37 »
I have been to the pub *beer* looks alright to me ,don't use brute force ,it hurts.

Offline Steverat

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Re: I'm smoking on the right too!
« Reply #49 on: 26.02. 2019 17:35 »
Made my own mandrel to check alignment of small ends, and guess what?
Haven't got the necessary parallels but a check with a straight edge acrosss the tops of both pistons confirms they are not tilted sideways.
Also reversal of the timing side piston does not affect the "leaning in the bore" phenomenon.

I decided not to try the hand tweak after all.
The Gandinis have arrived, in a state of high excitement now as I prepare to put them in and try the engine yet again....

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Online chaterlea25

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Re: I'm smoking on the right too!
« Reply #50 on: 26.02. 2019 18:02 »
Hi Steve,
Hopefully catching you before the barrels go on  *????*
If you have a vernier caliper, measure between the cylinders top and bottom and outside to outside of the bores
again top and bottom

This will at least check they are parallel to each other  *ex*
but will not check square to the base *sad2*

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Steverat

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Re: I'm smoking on the right too!
« Reply #51 on: 26.02. 2019 20:11 »
Hi Steve,
Hopefully catching you before the barrels go on  *????*
If you have a vernier caliper, measure between the cylinders top and bottom and outside to outside of the bores
again top and bottom

This will at least check they are parallel to each other  *ex*
but will not check square to the base *sad2*

John

Hi John
Yes I'll do it
Thanks
Steve

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Online Slymo

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Re: I'm smoking on the right too!
« Reply #52 on: 27.02. 2019 02:24 »
Really keen to see if the Gandini's make a difference. I replaced the oil scraper on the right hand side assuming that the oil from the leaking oil pump had stopped the originals (which were pretty new) from bedding in. Hasn't made the tiniest bit of difference so far I'm still producing a steady blue vapour. My plan is to put a few more hundred miles on the clock and see what gives then.
NZ

Offline worntorn

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Re: I'm smoking on the right too!
« Reply #53 on: 27.02. 2019 02:28 »
Are the Gandini's cam ground?
I've read and been told that this was a problem with GPMs back in the 80s.
Back then they were machined circular, no cam grinding was done.

Glen

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Re: I'm smoking on the right too!
« Reply #54 on: 27.02. 2019 06:29 »
I think it’s commonly accepted that a bent or distorted alloy conrod is scrap.

Offline Steverat

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Re: I'm smoking on the right too!
« Reply #55 on: 27.02. 2019 18:13 »
Smoke free day!!!

Yes we finally cracked it. Put the Gandini rings in, reassembled with heart in mouth, and hey presto, bike ran like a dream with NO SMOKE!

I refrained from any heroic con-rod bending exercises.

Thanks  to all of you who contributed comments and ideas. The Gandinis really are the business. I guess the other message is - watch out for Hepolite rings, even if they come in genuine NOS packaging. I will be calling the supplier tomorrow to discuss that, I'm sure they are innocent but someone along the line has packed the NOS package with rings which are wrong for the engine. Blueing up showed very heavy pressure against the bore at the ends of the rings and almost no contact at the opposing midpoint. Maybe the rings had been filed down to 71mm (70 +0.040") from something significantly bigger. The other immediately noticeable difference is the force needed to compress the ring. The Gandini compression rings close at 1400g applied radially; the so-called Hepolite NOS rings needed over 2000g because of their increased depth of section.

Josef will be pleased.

Steve

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Online berger

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Re: I'm smoking on the right too!
« Reply #56 on: 27.02. 2019 18:25 »
that's it then steve IT WAS THE RINGS loads of crap about mine blued up with high spots but the gandinis were all constant blueing----- glad you got there in the end its not fun keep taking them apart because of parts only fit for the dustbin . you deserve a *beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer* *yeah* *yeah* *yeah*

Online chaterlea25

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Re: I'm smoking on the right too!
« Reply #57 on: 27.02. 2019 20:46 »
Hi Steve
Glad to hear you have given up smoking  *lol* *lol*

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Steverat

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Re: I'm smoking on the right too!
« Reply #58 on: 27.02. 2019 22:30 »
Hi Steve,
Hopefully catching you before the barrels go on  *????*
If you have a vernier caliper, measure between the cylinders top and bottom and outside to outside of the bores
again top and bottom

This will at least check they are parallel to each other  *ex*
but will not check square to the base *sad2*

John

Yes they are parallel

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Online Slymo

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Re: I'm smoking on the right too!
« Reply #59 on: 27.02. 2019 22:49 »
Good news indeed although I feared slightly that the rings are to blame. The idea off pulling the top end down yet again doesn't hold a lot of excitement I have to admit. Moreover there is the profoundly annoying design flaw that sees me having to remove one stud from the rocker box in order to get it off the head when in frame. The B44 had the same issue so I guess they liked the gag at BSA design. Still a problem with an assignable cause is no problem at all!
S:)
NZ