A65 bolt and thread help

[Gordonh]

Hello all, can anyone tell me the bolt size and thread for the three bolts that hold the engine casing on the right hand side of the bike. The reason I ask is two of them seem to be stripped.What would the next size up be that I could use to re thread the holes or could helicoils be used and if so what size.Im new to A65s.

[chaz]

what year A65?

[Gordonh]

Hi it's a 1966 West Coast Hornet

[Bess]

Hi,
    I wouldn't helicoil but go to the next size up, others might say different.

If they 23 and 24 in the attached image  part numbers 15-2018 and 68-0018 they are 5/16" CEI.

Best wishes...

[Gordonh]

Sorry may be some confusion it's the 3 cross head screws/bolts that hold the outer right cover on which you take off to get at kick start return spring,2 at front and one at rear.

[chaz]

normally fit a free running helicoil on casing screws, trouble going bigger is you can go too big and/or loose the option of doing again if needed. Also from my point of view, I hate non standard fastners in casings, I bought an A7 off of a local "dealer", should have known better, on closer inspection the wood screws holding the cases on were pre cursor to the missing parts inside.

[Allan G]

Hi Gordon. Those screws are 1/4 BSF, I've had to helicoil most the screws on that side because
Someone at some point used the later UNC screws in my 68'.

As your probably aware those 3 pass through the inner cover and screw directly into the crank case. Uni-thread do a kit quite cheaply and the job is very quick to do, as the threads have probably failed you'll be able to go straight in with the thread tap, if your confident you can do these using a dril set to a low torque. Clean the holes out with IPA, acetone Or brake cleaner after Cutting the new thread and washout any filings. You can add a drop of locktite onto the helicoil before inserting which will ensure they never come out with the screw.

The only 5/16 bolts in the lower crank case section are those that bolt the two case halves together, them 5/16 nuts in the gearbox and cylinder barrel, the rest are 1/4"" and BSF at that.

[Bess]

Hi,
    Sorry in my first post, I as you said bolt, I referenced bolt, also I would have helicoiled not gone to the next size up. However as they are the outer case screws:

If they are as image ss1, item 17, they are part number 68-0229 see image ss2 and they are 1/4" CEI, see image ss3.

Best wishes...

[Gordonh]

Thanks for the help and advice going to go for the helicoil kit from Unithread,cheers Gordon

[Allan G]

The TPI for both CEI and BSF at 1/4" are 26tpi. Only difference being Cycle thread had 60° thread angle and BSF has 55°. The helicoils in mine are BSF, this hasn't posed an issue for the last 7 years.

[Bess]

Hi Allan,
            You are correct and many people have mixed fixings with success.

Your solution of mixing CEI and BSF fixings, or better still changing to completely to BSF,  probably even better change to UNC as BSA did. Maybe being controversial stick a metric in.

Best wishes...

[Allan G]

Agreed on that one, UNC is a much better thread for aluminium, Helicoiling works fine as your screwing into a steel insert but I think BSF is a problem thread, even the oil union bolt thread failed on mine, that was the first one that got repaired... I used a UNC Helicoil on that one and not looked back.

[chaz]

obviously changing a thread from standard (in parts books) could confuse future owners , you really would have to change all (both sides) of the casing screws otherwise , as always, the screws fall out or get moved and you risk putting the wrong bolt in the wrong hole causing more problems. personally helicoil like for like.
as for the threads themselves, BSC/CEI was always a bad move for the side casings, the thread of choice in practice would be a coarse (ie lower thread tpi) in ally, this stops the chances of threads stripping or cross threading due to over tightening , the more tpi, the thinner the  material between the threads, therefore coarser threads are better, BSC/CEI is ideal for thinner applications , body work or frame fittings in steel which is stronger and allow more thread contact.