- Joined
- Aug 8, 2005
- Messages
- 2,648
Jim,
Thanks. That is good to know.
Cheers,
Tom
CNN
Thanks. That is good to know.
Cheers,
Tom
CNN
comnoz said:Dances with Shrapnel said:Glad you posted this as a separate thread because I want to ask - what are the viable remedies other than the obvious "get a Fullauto head".
Would heating up the head and trying to extrude some JBWeld into the crack be a viable patch or just a bodge?
I don't think JB weld would do the trick. There needs to be enough strength to support the valve guide.
I have attempted welding but it took so much heat that everything was crooked when I was done and the head was too soft in the guide area to hold a guide. It machined like chewing gum.
I have a head on the shelf that I have welded up but never did the machining. I figured I would let it set for a few months and see if it got harder with age. It should be hard by now as that was about 10 years ago....
Dances with Shrapnel said:comnoz said:Dances with Shrapnel said:Glad you posted this as a separate thread because I want to ask - what are the viable remedies other than the obvious "get a Fullauto head".
Would heating up the head and trying to extrude some JBWeld into the crack be a viable patch or just a bodge?
I don't think JB weld would do the trick. There needs to be enough strength to support the valve guide.
I have attempted welding but it took so much heat that everything was crooked when I was done and the head was too soft in the guide area to hold a guide. It machined like chewing gum.
I have a head on the shelf that I have welded up but never did the machining. I figured I would let it set for a few months and see if it got harder with age. It should be hard by now as that was about 10 years ago....
So is it fair to say there is no good remedy for a cracked RH4 head as shown other than to bin it?
dynodave said:1. My opinion on why were the 750 guides 1/2" and 850 upsized to 3/4". Also as to why "upgrading to bronze" instead of 3/4" iron was not ideal either.
The shrink fit of bronze guides causes a squeezing of the guide and reduces the bore size. Now it has a waisted shape. when ever I ream the guides bore It only clears the center of the guide and the extreme tips which might be peened a bit by the tapping home of the guide. In this condidion you can not spot bore guage the hole. Only a full lenght dowel go/no go will approximate the "working" size.
If the guide is clear reamed all the way through the guide will be now "worn out big".
2. Possible bodge/bandaid for cracked RH4 heads. Clean the intake port crack using all solvents possible. gasoline, acetone, brake cleaner, methylene chloride followed by oil contamination removal with compressed air. After drying, seal the crack with "wicking" loctite 290 which is low viscosity and has a possible chance to penetrate and seal. Loctite should have a chance to hold up since the intake port should not be as hot as the exhaust.
Obviously clean the port crack before guide removal if you are going to do that, then repeat after installing new guide, then loctite seal.
lcrken said:Well, you can add me to the cracked RH4 group. I just checked the head on the MK3 that I'm rebuilding, and discovered the dreaded crack at one of the intake guides. Its visible without the need for dye penetrant checking. It looks about 3/8" long, but might be longer if checked properly. Supposedly, the bike had around 20,000 miles when it was torn down and put in boxes, which is how I got it. The other port doesn't show any cracks to the naked eye, and it didn't seem worth it to do the dye penetrant check. Fortunately I have an RH10 head off a race bike that looks pretty good, other than needing exhaust thread repair and stud inserts. More work for comnoz. I have another MK3 that I'm about to tear apart, hoping that the head is ok. Sure would be nice to find a method to repair these heads. Must be a lot of them out there by now. I would consider trying to weld it, but I haven't had really good luck trying to weld on Commando heads, other than for fin repairs. The castings tend to be really porous, and you can never seem to get all the oil out. Those Fullauto heads are looking better and better to me.
Ken
Diablouph said:I find the topic of a cracked R4 head depressing. As I read the posts it appears that there is really no fix which is considered "best practice" and permanent other that a Fullauto head of course.
If this is true, I would have to pay over half of the market value of my bike for a permanent fix, and the probability of it happening is fairly high.
Depressing.
Fast Eddie said:How would one detect the kind of cracks we areal king about here in a used bike? In other words, what are the symptoms, in use, of such cracks?
Fast Eddie said:How would one detect the kind of cracks we areal king about here in a used bike? In other words, what are the symptoms, in use, of such cracks?
Although mapp gas is hot enough to melt the repair rod, what is requires is the material your are heating/repairing to melt the flux and subsequently the rod. Oxy/acetylene is really needed to concentrate the heat to where it is need where you can facilitate the repair before heat disapation. If you can successfully braze a cast iron repair, you can surely handle an aluminum/aluminium repair.hobot said:Would the propane torch melt alu repair rods from Muggy Welding have application here?
http://www.muggyweld.com/
pete.v said:Although mapp gas is hot enough to melt the repair rod, what is requires is the material your are heating/repairing to melt the flux and subsequently the rod. Oxy/acetylene is really needed to concentrate the heat to where it is need where you can facilitate the repair before heat disapation. If you can successfully braze a cast iron repair, you can surely handle an aluminum/aluminium repair.hobot said:Would the propane torch melt alu repair rods from Muggy Welding have application here?
http://www.muggyweld.com/
Repairs of this nature are a step up from JB Weld and such repairs should be limited to filling holes, cracks, fins and such, and not for anything requiring structural integrity. Just sayin.
hobot said:Would the propane torch melt alu repair rods from Muggy Welding have application here?
http://www.muggyweld.com/
Dances with Shrapnel said:comnoz said:Dances with Shrapnel said:Glad you posted this as a separate thread because I want to ask - what are the viable remedies other than the obvious "get a Fullauto head".
Would heating up the head and trying to extrude some JBWeld into the crack be a viable patch or just a bodge?
I don't think JB weld would do the trick. There needs to be enough strength to support the valve guide.
I have attempted welding but it took so much heat that everything was crooked when I was done and the head was too soft in the guide area to hold a guide. It machined like chewing gum.
I have a head on the shelf that I have welded up but never did the machining. I figured I would let it set for a few months and see if it got harder with age. It should be hard by now as that was about 10 years ago....
So is it fair to say there is no good remedy for a cracked RH4 head as shown other than to bin it?