RH4 head crack symptoms

JimNH · Sep 21, 2015

MKIII with an RH4 that I suspect may be cracked. I'll probably pull it apart in the off season but I'd like to compare symptoms while it's still running.

What have others experienced before a teardown confirmed it?

cash · Sep 21, 2015

What makes you think it is cracked?

Dave

comnoz · Sep 21, 2015

JimNH said:
MKIII with an RH4 that I suspect may be cracked. I'll probably pull it apart in the off season but I'd like to compare symptoms while it's still running.

What have others experienced before a teardown confirmed it?

The normal crack is down the side of an intake guide from the spring seat area. Symptoms are similar to a bad valve stem seal, ie. smoking at startup and excess oil consumption. Jim

JimNH · Sep 21, 2015

comnoz said:
JimNH said:

MKIII with an RH4 that I suspect may be cracked. I'll probably pull it apart in the off season but I'd like to compare symptoms while it's still running.

What have others experienced before a teardown confirmed it?

Click to expand...

The normal crack is down the side of an intake guide from the spring seat area. Symptoms are similar to a bad valve stem seal, ie. smoking at startup and excess oil consumption. Jim

Thanks Jim,

That's what I have. No noticeable smoke while riding but plenty at startup. Sadly, there appears to be no permanent fix that I've heard of other than replacement.

Jim

comnoz · Sep 21, 2015

JimNH said:
comnoz said:

JimNH said:

MKIII with an RH4 that I suspect may be cracked. I'll probably pull it apart in the off season but I'd like to compare symptoms while it's still running.

What have others experienced before a teardown confirmed it?

Click to expand...

The normal crack is down the side of an intake guide from the spring seat area. Symptoms are similar to a bad valve stem seal, ie. smoking at startup and excess oil consumption. Jim

Click to expand...

Thanks Jim,

That's what I have. No noticeable smoke while riding but plenty at startup. Sadly, there appears to be no permanent fix that I've heard of other than replacement.

Jim

Well, You may just have bad valve stem seals also. The OEM seals are not too good. Jim

JimNH · Sep 21, 2015

[/quote]

Well, You may just have bad valve stem seals also. The OEM seals are not too good. Jim[/quote]

Ha! That's my hope

Torontonian · Sep 22, 2015

I'm hoping for bad old original intake seals too. I'll be pulling the RH 4 head on my new MK 111 in about a month after the season is done here. Symptoms are similar ,smoking on startup with gradual clearing , but it can start smoking at any time too , then clear up. Acquired an RH 10 and is ready to drop into place but am dreading finding this unfixable "crack" being discussed. :shock:

jseng1 · Sep 22, 2015

I'm looking for a couple cheap cracked heads that no one intends to fix.

Email jim@jsmotorsport.com

JimNH · Sep 22, 2015

jseng1 said:
I'm looking for a couple cheap (or free) cracked heads that no one intends to fix.

Email jim@jsmotorsport.com

Researching a fix?

jseng1 · Sep 22, 2015

JimNH said:
jseng1 said:

I'm looking for a couple cheap (or free) cracked heads that no one intends to fix.

Email jim@jsmotorsport.com

Click to expand...

Researching a fix?

See my post "Norton intake ports compared to Harley XR 750".

I'll be welding up stock ports to raise the floor, adding weld to the sides and center of the head so I can copy the 46mm wide x 27mm high (at the guide) "Narley" ports according to the Autocad plans I've drawn up. With so much welding I may as well hog out a cracked guide area and fill it in - and add some weld to thicken up the roof where its thin, Give the roof an efficient eyebrow shape to duplicate the 'Narley" port. Maybe work out the tool movements on a mill so I can repeat it or write a CNC program. Its a project.

cjandme · Sep 22, 2015

I've been following those threads too, and boy o boy what a truly awesome project Jim. My hat is off to ya!

Torontonian · Sep 25, 2015

You can have my RH 4 for the price of postage if it turns out unfixable crackage by inlet valve. You gotta wait till'I pull the head in winter !. Smokin'. ! :!:

RH4 head crack symptoms

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