Author Topic: My SRM conrod bolt nuts touch the casing and won't let the crank turn!  (Read 5598 times)

SRM

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Hello A7/A10 forum
we are concerned that owners maybe having problems with the ARP product supplied by SRM
specifically the ARP bolts supplied as OE replacement for standard rods.
The ARP bolts SRM supply are shipped with the bolt-specific instructions that come directly from ARP. I have been in contact with ARP who have confirmed that the bolt 14AG2.600-1, should be used in accordance with the supplied instructions.
As reflected in this forum, this is not always an effective solution for you guys so I have spoken to Geoff Dewhurst, SRM workshop manager, and he has measured a set of standard conrods, at various torque settings, to find out what was happening. The rods distort by about 0.001? at 37ft/lbs at a perpendicular to the joint face.
The original rods would have been torqued to 22ft/lbs and the big-end face honed to finish, in an ideal world the conrods would be assembled and torqued to the new ARP specification and the big-ends re-honed to suit the new bolts.
As owners probably prefer a straight fit Geoff pragmatically advises the following;
?We have found that in some cases these bolts (ARP) torqued to 37ft/lbs, may distort the con rod end-cap, resulting in a restriction of free rotation, accordingly, SRM recommend reducing the setting to 28ft/lbs with an application of thread-lock on the final tighten, remember the bolts must be tightened and relieved twice with tightening to final setting on the third attempt?
Geoff also adds;
?These bolts were originally for a Triumph application but are advised by ARP to work well on BSA rods. Check for clearance on the scavenge pipe casting (timing side crankcase) on the A10?.

We would like to assure owners that all correspondence with SRM is answered, our internet address changed approx 18mths ago to www.srmclasssicbikes.com and we apolgise if any emails were lost in this process.

If you would like specialist advice the SRM department heads are;
Jon Jolley, Electrical and wheel building                  jon@srmclasssicbikes.com
Geoff Dewhurst, Engineering and workshop            geoff@srmclasssicbikes.com
Gary Hearl, Stores and parts/model specific info      gary@srmclasssicbikes.com

SRM now have a dedicated department for new product design and development and we are working steadily to eradicate specific issues with any products we supply.

Regards

Patrick

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i got my box done by SRM and they quoted 2-3 weeks but it was returned within 2 weeks and a great job, hope yours is done as well and as quickly, Bob Hebdon.
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G'day Patrick, welcome to the forum.
                                                  Thank you for taking the time to investigate and report on the con rod bolts. Well done.
I never tried your tighten & relieve method and (touch wood) have never had a failure. But I will take that on board for next time.
Never too old to learn something.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline MG

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Hi Patrick!

Good of you (and SRM) to join us, great to have you here for direct communication/discussion. I hope you will be available here in the long run? I suppose you can get a lot of valuable feedback from this place.

Cheers, Markus
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Offline A10Boy

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Yes, Hello Patrick.
How about making some nice new Thick Flange barrels, or even some AJS / Matchless 650 cranks?  *smile*
Regards

Andy

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Offline t20racerman

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I'm very impressed that SRM took the effort to come on this forum and reply to my thread about the bolts. That is the sign of a good company, responsive to customer needs.
 *smile*

I've been using them on and off since 1985 or so and have always been impressed with their service (Main bearing conversion) and spares (loads!)
Thanks for responding guys, and in my own independent testing of the big end bolts I found that 30 ft/lb still caused a tiny bit of restriction, but 27 ft/lb (which I settled on) was perfect.
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SRM

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Thanks for the warm welcome gents, my department (Manufacturing, design, marketing) is a recent addition to the SRM business and I know I will be learning a great deal from owners such as yourselves.

Re the "thick flange A10 barrels", I won't be breaking any trade secrets to hint that we do have such a project "in the pipe" but as with most of our projects
we have to balance the financial return against the investment as projects like this are not cheap. Our international partners and distributors seemed luke-warm about the thick-flange-barrels and so maybe you guys can give me an idea/feedback about how many sets are potentially required?

Re the ARP bolt issue, a fuller tech explanation will be available on the SRM website under "Technical" by the end of the week

thanks again for the positive response

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G'day Patrick,
                   I'd be in for 2, and while your at it another '54 alloy head with SR big valves  *whistle*.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline A10Boy

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Yup, subject to price, I think there would be a demand, lots of the originals are now on +60 or fitted with sleeves.
Regards

Andy

1958 Super Rocket
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1974 Kawasaki Z1a
Yam XJR 1300

Offline LJ.

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A good indication to the price of newly made barrels would be to see just how much originals are exchanging hands on ebay! There are an awful lot of A10s still out there on the roads and many owners are not engineers, often we are asked where and whom can do rebores, of course SRM can undertake this.

Would be nice to have a 'package/kit' consisting of new barrels, pistons, rings etc for the average guy to do his own work. I'd certainly be up for one if they became available!
Ride Safely Lads! LJ.
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Even better would be to make them alloy and offer 750 kits just like the trihard ones!!
I'll take my pills now.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
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Offline Tomcat

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A good indication to the price of newly made barrels would be to see just how much originals are exchanging hands on ebay! There are an awful lot of A10s still out there on the roads and many owners are not engineers, often we are asked where and whom can do rebores, of course SRM can undertake this.

Would be nice to have a 'package/kit' consisting of new barrels, pistons, rings etc for the average guy to do his own work. I'd certainly be up for one if they became available!
  The kit sounds good to me, my barrels need fins welded on, a rebore (or liners) and then a couple of piston assemblies.
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Offline jjbsa

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A very interesting thread, and helpful to me!  I bought a set of the ARP bolts a couple of years ago, and only got around to using them on a newly ground -.010" crank early this year.  They touched the crankcase and the crank would not spin.  So I clamped the crank with the rods in in a vise and carefully filed off the interfering bit, with the nuts at the bottom so the filings would not drop down next to the rods.  Like another contributor, I had already found that approaching the full original SRM-quoted torque on the nuts started to make the rods show a resistance to turning freely on the crankpin, so I backed off a bit when they became free again, though the torque was still over the 28 foot pounds now quoted as correct.  Now fortunately the rebuild still isn't complete, so having in the meantime discovered the forum and read all this about about excessive torque I will take out the motor and retorque the big end nuts as stated in this thread.  I am impressed that SRM have joined in the discussion in a positive way.  Perhaps they might consider contacting people who have bought these bolts, mentioning the updated data for them - many sales must involve email where that could be done without much effort, after all.

Re the thin flange barrels: I don't think they are as bad as people say.  In the '60s I ran a home built RGS lookalike that would do 13.66 1/4 miles in road trim at NSA sprints and that had thin flange barrels.  I suspect that flange cracking on thin flange barrels came from the two halves of the crankcase not aligning perfectly at their top face and putting the flange on the barrels into too much stress. I have seen a number of crankcase sets that didn't align well - the ones on my bike had a step of about 2 or 3 thou until they were skimmed.

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G'day jjbsa,
                I blew 3 barrels off my '57 SS, cases were spot on. I think 13.5;1 comp and 8000 rpm had a bit to do with it !! *eek*
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline jjbsa

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8,000 is a lot of rpm!  That's Chris Vincent territory.  I'm sure thick flange barrels would be a good idea for that!