Hi guys I think it was SoCal250 who gave me the dimensions on spacers for Rd DG heads. I apologize for not storing the info. Was it 22/12/8 ?
I took stock head bolts and shortened them.
I am a firm believer that spacers on head bolts are a bad idea.
I didn't do anything. I just use the stock washers. I didn't even know they required spacers at the time.
If you measure the thickness of the head at the stud locations and compare it to a stock RD head, you will be able to decide if you need a spacer and if so how long it needs to be.
Alternatively, screw on stock OEM sleeve nuts without any washers and measure the amount that the heads are above the new heads (if at all) and add say 2mm to that dimension for the spacers.
When new, DG Performance heads came with steel spacers. It is very rare to find them included with a set of heads now because they've all been lost over the last 35-40 years. Obviously, they don't seem to be critical because there a lot of people currently running DGs without spacers.
http://www.2strokeworld.net/forum/index.php?topic=64.msg647#msg647
Hi perhaps they don't need spacers but I acquired another complete engine that had DG heads and they had spacers that were not DG but were trying to replicate the dimensions by adding washers to spacers to equal the dimensions that may have come with the heads originally.
If anyone is looking for RD400 DG head spacers shoot me a pm I have a set.
Quote from: bitzz on February 24, 2019, 09:30:41 PM
I took stock head bolts and shortened them.
I am a firm believer that spacers on head bolts are a bad idea.
Spacers, and overly long fasteners in the first place, will give a more elastic connection in any case. Which definitely is not ideal for a cylinder head. But can be very useful in other applications. Any bolt or screw connection that tends to vibrate loose, will improve a lot if using a longer bolt + a spacer.
Now that I pulled off my DG's I wanted to get closer to the correct spacers for the head bolts.
I currently had 3 washers, stacked, to approximately 5mm give or take.
I have found minor discrepancies between some old posts about the spacer dimensions.
Our "Tech Section" has "OD: 22 mm; ID: 12 mm; thickness: 8 mm".
There is a way-back post from the old forum that states " OD: 21 mm; ID: 8 mm; thickness: 7.5mm) posted here: http://www.eurospares.com/graphics/Yamaha/MX175B/Yamaha%20RD350_400%20aftermarket%20cylinder%20head%20info..pdf (http://www.eurospares.com/graphics/Yamaha/MX175B/Yamaha%20RD350_400%20aftermarket%20cylinder%20head%20info..pdf)
I don't think the 8mm ID makes sense, since a head bolt is 11mm, I'm staring at one.
In any case, 7.5 or 8m is awfully thick. 5 US pennies are about 8mm. Look at my washer stack, about 4-5 mm versus a stack of pennies at 8mm:
(http://i239.photobucket.com/albums/ff131/aaaltered468/Yamaha%20Rebuild/C6054D4B-8D4C-4325-9B64-E38DE8E4B354.jpg) (http://s239.photobucket.com/user/aaaltered468/media/Yamaha%20Rebuild/C6054D4B-8D4C-4325-9B64-E38DE8E4B354.jpg.html)
I really don't want to stack three washers when I put the heads back on. Does anyone have a source for a washer/spacer that thick? Or even 4 mm? Are the originals REALLY 8mm? Anyone have eyes on one in their stash?
The closest I can find while searching is at Grainger, m12 x 26 x 5mm thick.
https://www.grainger.com/product/GRAINGER-APPROVED-M12x26-00mm-O-D-5RU14 (https://www.grainger.com/product/GRAINGER-APPROVED-M12x26-00mm-O-D-5RU14)
I measured the DG pockets at 30mm so other m12 thick's I've found won't fit.
I have original dg head spacers I can measure up and make some for you if your interested.
Pm me.
Garrett
PM sent, it will be great to finally know the correct dimensions and have some made.
Ed
Garrett, PM sent.
Dimensions in the Tech Library are from measurements taken by a 3rd party in 2013. The 2009 data was not valid.
I was able to source spacers that will reasonably fit. Advertised as nominal 30mm od, 14mm id, 6mm thick, zinc plated. Got them today. Measures 29.2 mm x 14.8mm x 5.5mm. Given my old "stack" was less thick than that I should be golden....Now I'm just waiting for my head bolts to return from the chrome shop...
(http://i239.photobucket.com/albums/ff131/aaaltered468/Yamaha%20Rebuild/FFCAD41F-35FE-4383-B751-308783FCF121.jpg) (http://s239.photobucket.com/user/aaaltered468/media/Yamaha%20Rebuild/FFCAD41F-35FE-4383-B751-308783FCF121.jpg.html)
(http://i239.photobucket.com/albums/ff131/aaaltered468/Yamaha%20Rebuild/03F41DD1-D280-4216-A302-074D611AD186.jpg) (http://s239.photobucket.com/user/aaaltered468/media/Yamaha%20Rebuild/03F41DD1-D280-4216-A302-074D611AD186.jpg.html)
nice.
I ran washers on the rprd heads to keep the heabold from galling the head, its always a good idea. a washer, 8 mm to .020" wont affect elasticity one bit in this application.