XJ11 Exhaust stud bolts came out instead of nut unscrewing

[KA1J]

Curious what would be the best approach at this point... I'm removing the rusted manifold to clean off & paint with high temp SS paint. I used Kroil on the rusted Allen nuts to free them but when I removed the Allen nuts, three of the Stud bolts screwed out instead of the Allen nuts coming loose & off.

Also, a PO had replaced an Allen nut with a hex nut which measured to be a 1/2" nut & definitely not metric. It also came off with the stud unscrewing. (so I have 4 out of 8 exhaust studs that came out of the head).

I tried one of the freed Allen nuts on the threaded stud with the 1/2" nut stuck on it and it is a perfect fit, so the threads on this are the same metric as the others. I forget the # of the metric Allen wrench but it fits the nuts perfectly. Why a SAE nut would be on the metric stud I have no idea, it doesn't look like it was forced on mismatched threads but none of the metric wrenches fit it properly.

So with that:

What is the way to remove those stuck nuts on the studs now that the stud has unscrewed from the engine? I don't want to put the threaded ends in a vise & have at at the nuts for fear of damaging the threads. There's that little "no thread" area in the middle of the stud but I can't figure how to hold that with enough grab to let me use the Allen wrench to unscrew the nut.

How do you best install those studs or replacement studs back into the head once the Allen nuts are removed? Perhaps the best thing is to try & find new nuts and studs but I haven't found the local hardware store to have metric Allen nuts or studs.

Basic questions but ones I haven't dealt with before. I'd rather ask first than botch it up.

Thanks

[lee_dutcher]

try some pb blaster and let it sit over night... or heat always helped me....hope that helps

[natemoen]

If you can find studs replace them. Go someplace like Fastnal, they will have them.

Could get a couple nuts and jam them on good and tight, put it in a vice, and try and hear up just the nut you want off and twist. Could also use some parafin wax with the heat to help.

[KA1J]

try some pb blaster and let it sit over night... or heat always helped me....hope that helps

Hi Lee,

That Kroil http://www.kanolabs.com/ is really some awesome penetrant & I prefer it to pb blaster though PB Blaster does work very well. I'm thinking it penetrated down into the exhaust studs and made them easier to turn than the nuts & that's why the studs unscrewed instead of the nuts coming off.

Heats an idea but I'm still not sure how best to hold & not damage the threads on the studs.

[skids]

Replace the stud. Why would you want to keep the old one if the threads might be buggered. I had a couple of sets of 4-1 Jardines and one of the studs is a headed bolt due to the lack of space.

[natemoen]

That's what the two jam nuts are for. Jam the 2 nuts on and then put the 2 nuts in-between the give jaws and clamp down hard.

[LoHo]

That's funny...I had one hex nut on the #4 pipe, too. Was that standard? Are those hex nuts available somewhere? One of the things that surprized me was how easy they came off after all this time, given the horror stories of studs pulling out or (shudder!) snapping off. I've had the bike since '97 and I've never taken them off before.

[CaptonZap]

The thread is an eight mm by 1.25 pitch. You can use coupler nuts to replace any that are lost, or use bolts instead of studs.
I don't like that idea, since it puts wear on the aluminum head. CZ

[natemoen]

The thread is an eight mm by 1.25 pitch. You can use coupler nuts to replace any that are lost, or use bolts instead of studs.
I don't like that idea, since it puts wear on the aluminum head. CZ

and its more likely that you will strip out the threads in the head if you use bolts.

[cywelchjr]

and its more likely that you will strip out the threads in the head if you use bolts.

Yup, and and I'm not sure why some with with Jardines have one bolt instead of all studs like stock. All mine are the stock studs and there is no problem with clearance. I don't think the 4 into 1 would be any different. Of course mines the 4 into 2 spaghetti pipes, but I can't see how you could have anything different, as the exhaust ports don't move. Now I know that a couple of them are hard to get them onto with the hex tool, but with a little work I can get to all of them, and at least they all look the same.

[natemoen]

Now I know that a couple of them are hard to get them onto with the hex tool, but with a little work I can get to all of them, and at least they all look the same.

Or just get the long reach Allen sockets. Just got me a set today, they were on clearance at harbor freight!

[KA1J]

After consulting the XJCD it looks as the cross reference for Yamahas using these studs goes as follows:
Part # 95621-08615-00
Bolt, Stud M8-15L, #02749

SR500E 1978 500 SR500 Street
SR500F 1979 500 SR500 Street
SR500G 1980 500 SR500 Street
SR500H 1981 500 SR500 Street
TT500C 1976 500 TT500 Off-Road
TT500D 1977 500 TT500 Off-Road
TT500F 1979 500 TT500 Off-Road
TT500G 1980 500 TT500 Off-Road
TT500H 1981 500 TT500 Off-Road
XJ1100J 1982 1100 XJ1100 Street
XS1100E 1978 1100 XS1100 Street
XS1100F 1979 1100 XS1100 Street
XS1100G 1980 1100 XS1100 Street
XS1100H 1981 1100 XS1100 Street
XS1100LG 1980 1100 XS1100L Midnight Special Street
XS1100LH 1981 1100 XS1100L Midnight Special Street
XS1100SF 1979 1100 XS1100S Street
XS1100SG 1980 1100 XS1100S Street
XS1100SH 1981 1100 XS1100S Street
XT500C 1976 500 XT500 Dual Purpose
XT500D 1977 500 XT500 Dual Purpose
XT500E 1978 500 XT500 Dual Purpose
XT500E-205001 1978 500 XT500 Dual Purpose
XT500F 1979 500 XT500 Dual Purpose
XT500G 1980 500 XT500 Dual Purpose
XT500H 1981 500 XT500 Dual Purpose

I'm not sure what the "15L" in M8-15L means but it' part of the size &/or thread pitch.

Perhaps with this I can find new parts to fit. Don't know about the Allen Nuts but maybe SS hex nuts applied with anti-seize would be as good or better.

The bike has a 4-1 and the original hardware did not come with the bike. I am... trying to clean up everything with rust on it

[Lamric]

I'm not sure what the "15L" in M8-15L means but it' part of the size &/or thread pitch.

The 15L just means that the threaded part of the stud that goes into the head is 15mm long.

[natemoen]

SS does not take heat well and will not look so pretty after it has been heated up a couple times.

[KA1J]

SS does not take heat well and will not look so pretty after it has been heated up a couple times.

LOL, the existing Allen nuts are UGLY with rust. No matter what I do to them they're not going to be pretty. I was thinking SS (with anti-sieze) only for the non-rusting properties. The 4-1 unknown make (probably MAC) headers are 40% chrome & the top end is rusted. I've read about some SS ultra high temp spray paint which people have successfully used on their headers as a poor man chrome and I've thought that might be a good solution once I've removed the rust. That or black header paint. The bike is maroon though Connecticut DMV changed that to red... so a darker color on the headers wouldn't be an issue.

I'd rather have a clean original exhaust but I gots what I gots.