Author Topic: head work  (Read 1093 times)

andy230

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head work
« on: October 06, 2006, 07:54:11 PM »
Hi guys,

Sorry to labour the point!

I'm sorting the SRX head (finally!) this weekend.  Waited a while on parts.

Should I clean off the old carbon from the racer's head while I'm in there??  Will it actually make it flow any better?  Will it make any more power at all?

I'll lightly grind the old valves, and grind in the new one proper...

Just wondering if I should de-coke before bolting it all back together.  And is it theoretically better to polish (ie with brasso) the combustion chamber??

Have to say tho, the Slipsteam head work on the ports and round the tracts is lovely.  Quite a lot of metal has been taken off round the guides...

Cheers

a

themoudie

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Re: head work
« Reply #1 on: October 06, 2006, 09:27:29 PM »
Aye Andy,

Personally wouldn't bother with the 'bull', just clean carbon off with a lollipop stick and cocktail sticks. If there is more effort required than these will take to remove the carbon, are you revving it hard enough? ;-)

Opinion varies between polished mirror finish and clean unpolished surface. First assumes greater flow hence total volume of charge to burn. Second assumes 'golf ball' effect which provides lots of minor eddies in the charge giving better atomisation and mixing of the charge, hence a more complete burn of the charge. The shape of the ports has more effect than either finish on potential charge volume.

You also mention that a lot of alloy has been removed from around the valve guides. Whilst Slipstream know their stuff, I just wonder if too much has been removed, reducing support for the guides and allowing them to flex at high rpm. Common problem with over enthusiastic removal of alloy on Duke single heads in the inlet port, when trying to get them to breath properly. I don't think I need to elaborate on the consequences of flexing, loosening, valve guides at high rpm!!! :-O

Finally, after grinding in your valves, finish off with Brasso or Solvol to get really smooth seats. Wash away ALL traces of grinding/polishing compound. Smear seats with a touch of light machine oil before assembly and some graphite and engine oil on the stems to ensure they don't 'pick up' when first starting.

All the best, Bill

andy230

  • Posts: 1322
Re: head work
« Reply #2 on: October 07, 2006, 12:28:38 AM »
Cheers!

wont bother with polishing the chamber then.

Gave the old valves a quick grind, and the new one a wee bit more.

Noticed some pretty mild pitting on the exhaust valve and seats.  Didnt want to give it too much, but there are still marks.  Acceptible?? Am not getting seats and valves anyway!  But can these be removed??

Seemed to be going ok before...

And whats the opinion of after solvet cleaning to stick it in a dishwasher afterwards?  Or is that just daft?!

a

peterj

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Re: head work
« Reply #3 on: October 07, 2006, 08:38:06 AM »
I always end up doing a kero leak test. If it doesn't leak, I don't worry about pitting, if it does the grind some more.

The dishwasher ounds like a reasonable idea, but I'd be giving it a very good hand wash first to get at the bits the spray wont reach and probably more importantly minimise the risk of the missus finding out why the best china smells of 20/50............

themoudie

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Re: head work
« Reply #4 on: October 07, 2006, 09:14:01 PM »
Aye Andy,

As peterj says "I always end up doing a kero leak test. If it doesn't leak, I don't worry about pitting, if it does the grind some more."

It's in the grinding man!

By the way have you noticed how PC this forum is? I referred to a Cocktail stick in my previous message and it inserts asterisks. Non emasculated male bird next! ;-)

Cheers, Bill

andy230

  • Posts: 1322
Re: head work
« Reply #5 on: October 08, 2006, 08:28:49 AM »
Ey-op!


Crap day yesterday-

Chucked the head in the dishwasher with lots of fairly liquid.  Went for a shower, when I came out the kitchen was full of suds.   Like, about 2 feet of em!!

I had to scoop the foam out of the dishwasher.  It was entirely full and took ages.

And put it on 2 or 3 rinse cycles to get rid of em.

But got the head clean- came out nice!!!   :-)

**Question-  Can I try a leak-down test with petrol not paraffin???**

Day didn't get much better:

Went to go to the dump with the van.  Running lights off the inverter in the garage had flattened the battery.

Crap!

2 hours later, I got to the dump kust as they were locking the gates.  "Come back tomorrow mate"


AAAaaarghhh!!!


Next, I reversed into a parked car.  That made my day, really.

Still, at least the skorp's good...  (touch wood).

Cheers

a

andy230

  • Posts: 1322
Re: head work
« Reply #6 on: October 08, 2006, 08:31:40 AM »
AND....

How long should the head hold liquid for.  (Petrol or paraffin?)

I did the head gasket recently on the 750 Norton.  Rather than strip the head, I was satisfied when paraffin didn't leak overnight.  Does it need to be this long??

Cheers again!

a


Steve H

  • Posts: 1845
Re: head work
« Reply #7 on: October 08, 2006, 08:48:45 AM »
I pour petrol into the inlet and exhaust ports (not at the same time), if the combustion chamber is still dry after 10-15 minutes its good. If the seal is poor is usually leaks immediately.

andytwothirty

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Re: head work
« Reply #8 on: October 09, 2006, 08:41:44 AM »
No leaks overnight!  Ha!  Success!

May actually get the head on tonight...

Cheers for info.  FYI, I'm going for a standard Yam gasket (its only a 1mm overbore), and I'm just about to find out the recommended torque settings. Will post if diffrent from standard.

Dishwasher is to be recommended as an impromtu parts washer!  Note, excessive use of fairy liquid results in an explosion of foam over the kitchen.  Oven is good to dry it once clean.  (She was away visiting her mum) 

a

ps.  Cleared my history & cookies.  Now I have to sign in!  Gaaah

Steve H

  • Posts: 1845
Re: head work
« Reply #9 on: October 09, 2006, 08:59:29 AM »
Once logged in it should retain it