Replacing downpipe studs with bolts

[scwirral]

I've removed the studs from the exhaust ports on my engine in my CB-1 (its an NC23 CBR400 engine).

They are rusty and tatty, as are the dome head nuts. Any reason why I shouldn't just replace them with stainless bolts? Do the studs allow for expansion in some way, or is the idea just that it is easier to align the downpipes onto the eight studs before tightening the nuts, whereas getting all the bolts in would be more tricky?

Engine is out of the frame at the moment.

Cheers for your advice, guys!

[zimm]

i've used stainless cap-head bolts in the past, works fine.. just copper-slip 'em.

i think the idea with studs is that by just taking the nut off you arent wearing/risking the thread in the head, but that goes out of the window once the bikes a few years old anyway as its pot luck wether the nut comes off or the stud comes out.

[TriGGer]

Studs tend to be used for longevity, simply put you screw a stud into the alloy head once, whereas a bolt when inserted & removed from the head causes more stress/wear on the alloy thread. Added to the heat cycles, this can reduce the life of the thread in the alloy head. Using a stud solves this problem. If possible replace the studs with stainless iron equivalents and use stainless steel nuts.

HTH

[scwirral]

Thanks, guys. Good stuff as always. Now where's that thumbs up?

[banoffee]

I always try to fit spring-fit downpipes so that once you've fitted the flanges once, system removal for polishing, jacking the bike up etc only needs a few springs removing

[Number 6]

Hmmmmmmmmmmmmmm flanges (insert drool smilie)

[billysbones]

i've used stainless cap-head bolts in the past, works fine.. just copper-slip 'em.

i think the idea with studs is that by just taking the nut off you arent wearing/risking the thread in the head, but that goes out of the window once the bikes a few years old anyway as its pot luck wether the nut comes off or the stud comes out.

Yes. but don't use copper slip on stainless bolts. It corrodes them. Nickel paste is better. will post exact spec another night.

(and it's the right colour)

[gregtrx]

I think my bandit came from the factory with cap head bolts not studs. And a stupid mild steel bit on the end of the stainless collector that fell off and leaves my exhaust bodged and blowing.

[zx6rrob]

I think my bandit came from the factory with cap head bolts not studs. And a stupid mild steel bit on the end of the stainless collector that fell off and leaves my exhaust bodged and blowing.

I`m pretty sure Bandit mania (?) repair the collector boxes. Or you culd just do what I did with mine and get a stainless fabs mate to weld you in a new piece for a couple of pints...

[gregtrx]

I`m pretty sure Bandit mania (?) repair the collector boxes. Or you culd just do what I did with mine and get a stainless fabs mate to weld you in a new piece for a couple of pints...

Both are true, the bandit mania fix i pricey, £85 + post and that and welding will require me to take the bike off the road for a bit, so hasn't happened yet.