Honda-SOHC

SOHC.co.uk Forums => CB350/400 => Topic started by: Fleabie on June 18, 2024, 02:58:32 PM

Title: Re-plating crankcase bolts
Post by: Fleabie on June 18, 2024, 02:58:32 PM

Hi, I am getting ready to replate my crankcase bolts in zinc using a Gateros kit. The instructions say that if you have high tensile bolts, you need to use a slightly different cleaning process to avoid "hydrogen embrittlement".

Does anyone know if the original crankcase bolts are high tensile ? I have searched high and low for a definitive answer but I haven't found one yet.

For the 10 bolts that are torqued down and secure the crank in the crankcase, 4 of them are unmarked and the other 6 longer ones (see picture) are marked with what looks like a '9' (or maybe a backwards 'P' or maybe even a lower case 'b'!)

Thanks
Bill.

Title: Re: Re-plating crankcase bolts
Post by: Nurse Julie on June 18, 2024, 03:22:43 PM

It's a 9. But I'm not sure that's the tensile strength or not as I thought they were 8.8's, which is almost 9 I suppose🤔🤔🤔. We've always had ours re zinc plated, after us cleaning them and never had any issues.

Title: Re: Re-plating crankcase bolts
Post by: AshimotoK0 on June 18, 2024, 05:22:54 PM

I always strip high-tensile bolts and spokes with my Witches Brew described on this forum. Its alkaline based and much more gentle than Hydrochloric acid. I will try to get link.

Title: Re: Re-plating crankcase bolts
Post by: AshimotoK0 on June 18, 2024, 05:27:44 PM

http://www.sohc.co.uk/index.php/topic,8172.msg55137.html#msg55137

Title: Re: Re-plating crankcase bolts
Post by: Fleabie on June 18, 2024, 07:46:03 PM

Thanks to you both for the replies.

Ash: Do you just use your witches brew for stripping every type of metal, be it high tensile or other? I.e. play it safe and just use your brew?

Also, Do you know if the crankcase bolts are high tensile?

Cheers

Title: Re: Re-plating crankcase bolts
Post by: McCabe-Thiele (Ted) on June 18, 2024, 08:20:12 PM

I do not know the definitive answer but my thought  process is that the ten bolts are essential crank main bearing bolts as opposed to the remaining crank case bolts that just secure the casing halves. Grade 8.8 is high tensile

Generally speaking crank case bolts would be high tensile.

Title: Re: Re-plating crankcase bolts
Post by: AshimotoK0 on June 18, 2024, 09:16:25 PM

Quote from: Fleabie on June 18, 2024, 07:46:03 PM

Thanks to you both for the replies.

Ash: Do you just use your witches brew for stripping every type of metal, be it high tensile or other? I.e. play it safe and just use your brew?

Also, Do you know if the crankcase bolts are high tensile?

Cheers

I mainly use it for spokes. I agree with Julie ..normal acid stripping OK for no9 crankcase bolts.

Title: Re: Re-plating crankcase bolts
Post by: Fleabie on June 19, 2024, 07:29:42 AM

Thanks all. Much appreciated as usual 🙂