Author Topic: Preparing to rebuilt 61' Super Rocket Engine  (Read 986 times)

Offline adunham1

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Preparing to rebuilt 61' Super Rocket Engine
« on: 29.09. 2019 01:01 »
Hi everyone,

I'm getting ready to rebuild my 61' SR engine and was hoping for some advice on things to look out for, things to change/inspect "while I'm in there," and anything else related to re-assembly. Currently it's completely apart and I've got some anxiety about seeing all the bits laying around! It has already had the sludge trap replaced with SRM Allen head caps.

Currently I'm planning on new 8:25:1 +.040" pistons as the current bores are just a bit too large for the current .030" pistons. Probably GPM or Gandini (are they the same?). It seems my alternative are JP pistons, which are notoriously heavy. I don't mind sending the crank to get balanced, but would prefer not to if the new pistons are similar weight. Speaking of the bottom end, as long as I don't see any cracks or other signs of wear, is it OK to re-use the old con rods? New big and small end bearings, though.

Other than that, the bronze bushings for each side of the crank look OK, so I wasn't planning on doing anything there.

This is my first time really into the bottom end of a BSA, so I'm definitely a little apprehensive and want to make sure I take my time to do it right. Sorry for such an open ended question!

Other than that, I need to find someone in the US to rebuild the Magneto. The bike will be converted to 12v electronics, an SRM oil pump, external filter, and some Eddie Dow front fork parts.

Again, thanks for any insights you might be willing to share. I would really appreciate it!

Online KiwiGF

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #1 on: 29.09. 2019 01:32 »
Some weights of pistons are given in this thread link below, JP are not particularly heavy? Some manufacturers make one size of casting then machine them down, which means the over sizes are particularly heavy, but not the std size. Note some gudgeon pins can weigh a lot!

https://www.a7a10.net/forum/index.php?topic=6086.msg41598#msg41598



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Offline muskrat

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #2 on: 29.09. 2019 02:54 »
G'day Andrew.
Replace the anti siphon ball & spring.
Check the cam bushes, cam journals and lobes, cam followers for wear.
Old rods are OK if straight and crack tested (I polish mine). New bolts would be good.
Drive side main should be a C3 grade. Replace the timing side bush with a solid one and line ream to suit crank journal and check the crankcase hole for out of round (if it is a new bush has to be made to suit.
Trial fit crank in cases (without the cam) to check end float and shim behind the inner race.
That'll keep you going for a day or two.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online ironhead

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #3 on: 29.09. 2019 04:33 »

Old rods are OK if straight and crack tested (I polish mine). New bolts would be good.


Also make sure the big end holes are round & to correct size. They can be elongated ( stretched/ out of round)
SA

Offline bikerbob

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #4 on: 29.09. 2019 10:24 »
Muskrat has correctly detailed the important things to look at, I  would lke to attach great importance to his first line the anti syphon ball and spring this is behind the small screw inside the crankcase next to the timing side main bearing, but make sure you get the correct parts mainly the spring. This ball and spring does to some extent help with wet sumping, in my case on my A7 before I renewed them I had to drain the sump once a week or I ran the risk on start up of having oil come out of the breather onto the garage floor. After renewal  the bike does still wet sump but I have left it for over 3 weeks  and started it without oil coming out or smoke from the exhausts.

Offline Swarfcut

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #5 on: 29.09. 2019 10:57 »
 To add to former posts, new nuts and big end bolts are desirable but pricey. Existing Bolts are probably OK for further use, it depends on the nuts previously used, some locking types ruin the thread for further use. The problem with new ones are that many are not up to the job, even from trusted suppliers. As ironhead recommends, get the big end eyes checked for ovality. Any machine shop can do this.

 The basic weakness in the design is the oil feed to the big ends, using the timing side bush to feed oil into the crank. The bush needs to have a good seal around the periphery where it mounts into the crankcase, a leak here will vent oil, rather than it going into the crank. Wear on the bush and crank journal will also reduce the oil to the big ends. Suggested running clearance here when new is 1-1.5 Thou. Plenty on the forum about this bush, choices, modifications, installation, sizing.

  The sludge trap on your later crank is a removable tube. Folks take out the plugs, clean the hole they can see, leaving sludge on the outside of the tube. Remove the flywheel radial bolt and the tube will come out, revealing more sludge. The radial bolt should be replaced with a new one, Loctited in place for security, as a failure here wrecks the motor.

 The wear limit on the journals is 2 Thou, they usually wear oval, so measure diameter in several places, and each side for taper. If the big end journals are reground, remove the sharp edge around the oil feed holes, blending them into the journal surface, otherwise they can cut a neat groove in your new shells. Con rods are the same forging, drive side/clutch side one has a small bleed hole from the big end eye, this should face to the flywheel, putting the bearing shell tab slots on the rods towards the front of the engine.

Pistons and rings.... Hepolite pistons, now distributed by Wassell, and only related by name to the originals, have yet to establish themselves as a viable alternative, so are best avoided. New old stock AE/Hepolite are OK, they were the standard when the bikes were new. Gandini rings have a good reputation, curing oiling and smoke problems when fitted to pistons otherwise considered to be at fault. In your part of the world, Hastings rings would be a good choice.

 The small ball in the valve on the scavenge pipe in the sump needs to have reasonable movement, the ball often gets stuck by carbon and sludge, and the pipe needs to be secure and sealed into the crankcase.
BSA Service sheets are available in the Literature Section of the forum.

Good stuff there from birthday boy Musky.

Swarfy.

Offline Greybeard

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #6 on: 29.09. 2019 10:59 »
Has anyone mentioned cleaning out the sludge trap, (in the middle of the crankshaft)?

Swarfy got his post in before I posted.

Offline Swarfcut

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #7 on: 29.09. 2019 11:14 »
Hi GB, tried here to pass on some  hard won experiences......All the best.

Offline adunham1

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #8 on: 30.09. 2019 03:31 »
Hi guys, sorry for the late reply and thank you for all of yours!

I got nervous about re-using old rods and seeing as how I only want to do this once (hopefully!) went ahead and ordered some MAP cycle rods: http://www.mapcycle.com/performance-parts/connecting-rods/map7068-a-bsa-a10-late-4340-h-beam-connecting-rods-6-5.html I think I'm going to pair them with some 8.25:1 GPM pistons from wherever I can find them. TMS Nottingham seems to have them.

KiwiGF, that's a very informative thread. Thank you for sharing. I was messing about with weights and balance yesterday, but this is sort of a comprehensive guide so that's great. I will use this closer when the new bits arrive. I'll try to post an update with the weights of my new pistons, rods, etc when I get them.

Muskrat... you're right that'll keep me going for a day or 2, or 10! I've heard the solid bushes are a good replacement. Do you know of a good source for one? I've got a couple of good machinists that could do the work for me. Pardon my ignorance, is that C3 grade Bronze?

biker bob, yes I have read quite a bit about the anti-wet sump valve on many BSA models... so I guess I infer its importance. I had seen them on SRM's site, but do you think any NEW one would be fine or is there a preferred one? I'm not trying to break the bank here, but I want to fit good quality parts while I'm in this far.

Swarfcut, great name! I actually just re-assembled my crank with the new sludge trap this evening. I did NOT replace the bolt (but I have new ones... doh!) Interestingly enough, someone had cleaned the sludge trap recently as there was little to nothing in there. That was a little annoying, as it was the reason for pulling the engine! I will remove the bolt, replace it and loctite it in. Thanks for the spec on the timing side bushing, I'll relay this to the machinist that works on it. I had no idea about the ball in the scavenge pipe. I will have to take a look and research that a bit.

Thanks again everyone. I'm really looking forward to making some real progress! My Dad is helping me, so I'm sure he's excited to have it off his bench. This is only our second full engine rebuilt. We rebuilt a 1974 Moto Guzzi Eldorado last year, so it's very interesting to see how things are different, yet all the same.

Online Billybream

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #9 on: 30.09. 2019 04:38 »
C3 denotes internal radial clearance of mains roller bearing.
The A10 engine was stripped and rebuilt using basic tools and facilities and are fairly bullet proof, they need regular engine oil changes and need to be ridden with respect like you would treat any old girl.
I would try to reuse as many original parts as possible, certainly theres some rubbish pattern items now available. SRM are a very good source for new replacement items and offer support and backup.
1960 Super Rocket, owned since 1966, back on the road 2012 after being laid up for 29yrs.

Offline duTch

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #10 on: 30.09. 2019 06:12 »

 
Quote
.............Pardon my ignorance, is that C3 grade Bronze?...

 In addition to B-b's comment, my take on that is the clearance between the rollers/ balls, and the inner/ outer race(s)...

 
Quote
......... We rebuilt a 1974 Moto Guzzi Eldorado last year, so it's very interesting to see how things are different, yet all the same. ....
Well- that sure garnered my attention... I'd be really happy if our A10's were that easy...I did my model T in ~'96 and totally stoked; there must be a way.....



Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline adunham1

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #11 on: 30.09. 2019 14:33 »
Here are a couple of photos of the bike finished.



And yes, I wish they were as easy! Everything easily accessible and straight forward. The hardest part was learning some Italian to know which way round to put some parts!

Offline duTch

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #12 on: 30.09. 2019 16:56 »

 
Quote
........The hardest part was learning some Italian to know which way round to put some parts!...

 That's a bonus- just think of the mayhem you can acheive on your next Euro trip *smile*
The bit that baffled me is the ignition- red for right and green for left....me thinking it must be to do with navigation colours from their aviation background, but that went west when saw airplanes overhead with red left and green right....(I'm obviously not a boaty even though I did a navigation course)...turns out it's to do with the flag- but my argument is it depends which way I look at it  *pull hair out*

 Looking at the centre stand, it looks a fair bit far forward which would be loading the pivots up a lot and also not lifting wheels high enough- I had that on my T, so built up the stops with some 'trick' welding *work*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Online edboy

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #13 on: 30.09. 2019 20:46 »
my tip would be to ream out the conrod bolt holes . no binding or tight spots. reuse good conrod bolts.

Offline adunham1

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Re: Preparing to rebuilt 61' Super Rocket Engine
« Reply #14 on: 01.10. 2019 04:28 »

 
Quote
........The hardest part was learning some Italian to know which way round to put some parts!...

 That's a bonus- just think of the mayhem you can acheive on your next Euro trip *smile*
The bit that baffled me is the ignition- red for right and green for left....me thinking it must be to do with navigation colours from their aviation background, but that went west when saw airplanes overhead with red left and green right....(I'm obviously not a boaty even though I did a navigation course)...turns out it's to do with the flag- but my argument is it depends which way I look at it  *pull hair out*


HA! Just imagine me running down the streets yelling, "SINISTRA O DESTRA?!" (left or right!) over and over again.

Perhaps you have an ultra rare MEXICAN Guzzi? I can't remember what the stock wiring was; we ended up fitting a custom wiring harness with an alternator upgrade replacing the old magneti marelli generator.