Rusted exhaust studs.

[sp838]

Hello all. So, the latest discovery while going over my bike, cleaning, fixing, upgrading stuff, is that the acorn nuts are welded onto the exhaust studs with rust. They turn in the threads when I try to remove the nuts. Provided I can get them all out without breaking them off, I'd like to replace them, preferably with stainless steel. And instead of acorn nuts (which can trap moisture) I was thinking of using aircraft open nuts with built in teflon washers. Does anyone have experience with this? Thanks!

[docc]

I don't think the Teflon will sustain the exhaust temps. But others will chime in who know best.

[gstallons]

1. Will the nuts turn but not come off ? You need someone that is VERY good with a torch to heat them up to where you can remove the nuts. Then you will have to chase the threads with a die to clean the threads. Use new nuts, washers, etc. along with anti-sieze on the nuts. No nylon insert locknuts. I don't think the nylon will outlast the heat.  

[sp838]

The whole stud turns in its threads when I attempt to loosen the rusted-on acorn nuts. The nuts don't budge. I took one stud out completely, held it in a bench vise to try to get the nut off (no heating or lube just brute force) and it wouldn't move. So I cleaned up the threads a little, put on some anti seize and put it back on the bike. I don't wNt to bother with cleaning up the old studs, I want to replace them, preferably with stainless. I underatand the concern with the nylon lock nuts. Is there any reason why I shouldn't use standard open nuts with lock washers? I have a set of stainless acorn nuts, ready to go. But those trap moisture, if possible I'd rather not use them.

[gstallons]

The acorn nuts are for looks only. You can purchase new studs at any parts store.

[sp838]

Does anyone know off hand what size/pitch/length these are? I'd like to order replacements, the sizes aren't listed in the parts catalog. I'd like to not have to remove the studs to measure them before doing the actual job. Just ordered new exhaust gaskets, was going to wait till I had everything needed to do the job before taking it apart. I'm guessing they're M8x1.25, no idea what the lengths of the threaded portions are (they look to be of equal lengths in the parts catalog drawings), or what the length of the smooth middle section is. Worse comes to worse, I'll remove the one I got out last night and measure off of it. Thanks for your help thus far!

[gstallons]

the pitch is correct. Measure the old one to verify the length. The stud will not protrude into the acorn nut any farther than the flat of the nut.

[sp838]

So, in case anyone is curious, the measurements are: 12mm for the exterior threads, 15 mm for the smooth shank, 16mm for the interior threads. Diameter of the threads is 8mm, the shank is 7.5mm

 

I removed the header, just to take a peek at the exhaust gasket, and lo and behold! There is no gasket in there. So this is probably a good thing. I didn't check the other side, but no reason to believe that it should be any different. Stuck my fingers in there and there is a lot of black dry powdery carbon in there... The valve felt pretty much coated in crust. Is this normal?

 

Now I'm off to the internets to see if I can find these studs in stainless. First stop is arp-bolts.com they seem to have a pretty wide selection. I'll report back with my findings.

 

FOLLOW UP: ordered from jegs.com They have the arp bolt kit, which includes 12 point open nuts and washers. The studs have allen sockets on the end to facilitate installation. Pricey, at $42 for the four studs, four nuts and washers. Seems to be very high quality and arp are a reputable manufacturer of high performance fasteners etc. Can't wait to get them installed, a little nervous about removing the old studs... 

[gstallons]

You can jam 2 nuts together to get them loose and remove them .

[moto fugazzi]

I'd put as much penetrating oil as you can for a few days to try and get the studs and nuts off. Wouldn't hurt to heat them up like gstallons recommended. You're kind of screwed (or un-screwed) if one of those studs breaks off in the head. I broke one years ago, and tried an easy out which just shattered in the broken bolt. Not a fun time-nearly impossible to drill out at that point.

Good luck with the project and keep us posted.

Ken

[vuzzi]

I removed the header, just to take a peek at the exhaust gasket, and lo and behold! There is no gasket in there. So this is probably a good thing. I didn't check the other side, but no reason to believe that it should be any different.

 

 

Beter double check the exhaust gasket. They can be 'merged' with the cilinder head, that is, they can be hard to notice. Scrape along the edge with a knive or screw driver and maybe they will come off.

[sp838]

Will do! It's pretty gunked up in there, so I will absolutely clean out as much crust as possible and quadruple check to find the old gaskets and remove them. I'm thinking that at some point I will want to look into tuning the fueling system, and possibly ugrading to a Power Commander. One step at a time though...

[sp838]

Done! The rusty studs came out easily. Turns out there were gaskets in there after all, really crusted up and they had some surface rust too. Not pretty. Cleaned the threads out with wd40, a tap, and carb spray. Put the new studs in with some nickel based anti seize (they're stainless, didn't want to have them gall or break threads, didn't want to use thread sealer and never be able to get them out.)

 

Cleaned the inside of the ports out as much as possible, but I didn't want to abrade or score the mating surface so I went easy on them. Put some silicone sealant on the inside of the gaskets. Then buttoned it all up.

 

I torqued the nuts down to 15lbs. Didn't want to over do it and risk breaking threads. The nut on the under side of the header is in a real awkward spot. Can't really get a ratchet let alone a torque wrench in there. So I tightened both of them with a spanner by feel, as best I could.

 

Took her out for a spin after and all seems well. No signs of exhaust blowing out anywhere. So, on to the next rat's nest... Thanks for your help guys.

 

Edited to add: why does the, official no less, workshop manual suck so much? The instructions amount to this: "take it apart, then put it back together again." No mentions of torque. Or measurement of wear. No indications for the sizes and thread pitch for fasteners. The workshop manuals for my early '70s Hondas are better than this. The manual for my '86 Yam srx600 lists every single nut and bolt on the bike including the torque for each one. The v11 Sport manual is anxiety inducing in its lack of detail. Maybe Italians are just born knowing everything about maintaining these bikes... ?

[docc]

True that the Japanese manuals are much more detailed often with detailed diagrams in each section with torque references.

 

Also that the Japanese likely don't drink as much wine as the Italians. Especially between, say, lunch and the end of the work day. I'm not sure if there is a correlation there . . .

[fotoguzzi]

I wonder if the reason stainless is not factory in that application has a reason? like heating cooling between the stainless and aluminum head? also the softer aluminum threads will strip before the stud thread, reason for concern?