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Thread: ISO Dirt Wheels article for Ascott 500 Head Install

  1. #1
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    ISO Dirt Wheels article for Ascott 500 Head Install

    "Mickey Dunlap" mentions the article in his thread for new Big Bore 350x piston kits.

    Quote Originally Posted by Mickey Dunlap View Post
    Well I know about using the Ascot head because I did a magazine article on that back in the 90's in Dirt Wheels.
    During the forum search "Swigin" also mentions the article...in his Ascott 500 Head swap.

    Quote Originally Posted by SWIGIN View Post
    iv heard about this head swap way back in the late 80s or real early 90s when dirt wheels ....
    Yes I have the XL500 head on my 350x, runs great, built it around late '87-88, but I'm not going to disassemble that motor just to collect all the info needed to build another if I don't need too. That was over twenty-five years ago and my memory fails me....I've looked though all the Dirt Wheels Magazines I have, handful of late 80's early 90's and from February 95 to the present time no luck. Hope someone could provide me the correct month/year issue needed or copy of the article.

    "HJ" Click image for larger version. 

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    ’84 YT60
    ’85 350x (423cc) with ’81 XL500 head conversion
    ’83 XR500 (628cc) converted 3 Wheel hybrid
    ’73 CB750 K3 converted 3 Wheel hybrid
    ’86 TRX250R chassis XR650L engine hybrid
    ’89 TRX250R (stock )
    ’90 LT500 Quadzilla
    ’85 FL350 Odysses ( water cooled head )
    Lost (sold) but not forgotten ’80 ATC 110 (205cc on alcohol ) ’83 200x ( 222cc ) ’83 200x ( 185s eng ) ’85 350x ( stock )
    added to the collection recently, (2) '70 US90 Aquarius Blue and '74 ATC90 Daytona Orange

  2. #2
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    Hey Harry I have several Dirt Wheels from the late 80's through the mid 90's. I will see if I can find it.
    Also the XR and Ascot head are a little different. The Ascot has wider exhaust ports. I think the bolt on the same.
    * 1978 ATC 90/180 Pauter PJ1 / Springer "Team BAPP" Bike *

    * 1980 ATC 110/180 "Danny's Machine Works" 3D Sprint Dune Bike *

    * Nicholson 500 Race Bike *

    * HPATC Yamaha RD350 "Big Moe" Trike *

  3. #3
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    Yea the main bolt pattern is the same I have a ascot and xr/xl 500 heads off cause I always planned to do that swap one of these days
    If its on the internet its got to be true they can't put any lie's on the internet

  4. #4
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    Thanks Joseph, I have what I believe is the XL500 head installed on my '85 350x and I used the stock 350x head pipe back then. My high school buddy says he has 500 head that I could have and build another motor. When he gets it to me I'll use a stock head pipe and check exhaust port width. Sam Coe told what to do basicly but can't remember every thing I did.

    "HJ" Click image for larger version. 

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  5. #5
    Billy Golightly's Avatar
    Billy Golightly is offline Always finding new and exciting ways to not give a hoot in hell Catch me if you can
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    I have a complete ascot I hoped to do this with one day but you know how that goes. The head bolts right down on the 350x cylinder, I do remember that much. I think you need a little longer cylinder studs (possibly from 400ex?) I remember SWIGIN did this swap years ago and did have a pretty documentation of it at the time, I'll see if I can find it.

  6. #6
    Billy Golightly's Avatar
    Billy Golightly is offline Always finding new and exciting ways to not give a hoot in hell Catch me if you can
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    Harry you got lucky and I remembered the name of the thread - http://www.3wheelerworld.com/showthread.php?t=78141 it's not the dirt wheels article but I bet it helps out

  7. #7
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    Here is what I found. It doesn't go into much detail. I assume this is the article.

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    * 1978 ATC 90/180 Pauter PJ1 / Springer "Team BAPP" Bike *

    * 1980 ATC 110/180 "Danny's Machine Works" 3D Sprint Dune Bike *

    * Nicholson 500 Race Bike *

    * HPATC Yamaha RD350 "Big Moe" Trike *

  8. #8
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    thanks Billy for the link, read though that thread (all 10 pages) again yesterday before posting this request. Google search back in 2013 lead me to "Swigin"'s thread as a guest, that's when I registered into this forum and met all the cool guys here in the San Diego area. Some of what I do know is only welded one small boss on the 500 head cover for the oil feed connection. My reluctance to disassemble my motor is the head gasket (made of copper), unknown availability and mods made to it. If I do disassemble I'll take lots of pic's and post.......

    "HJ" Click image for larger version. 

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  9. #9
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    thanks "Joseph" I have that magazine issue (March '95) but believe the article he talks about goes a little more in depth. I know Mickey pops in the forum to read his threads, hopefully he'll comment to whether that's the article he spoke about in his Big Bore Piston thread. I'm going to attach the cover page as Mickey mentions a white 250r and red frame.

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    "HJ" Click image for larger version. 

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  10. #10
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    Quote Originally Posted by HairyJR View Post
    thanks "Joseph" I have that magazine issue (March '95) but believe the article he talks about goes a little more in depth. I know Mickey pops in the forum to read his threads, hopefully he'll comment to whether that's the article he spoke about in his Big Bore Piston thread. I'm going to attach the cover page as Mickey mentions a white 250r and red frame.

    Click image for larger version. 

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    "HJ" Click image for larger version. 

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    Yes that's the one, but that head is not the way to go if you are starting from scratch building one. The combustion chamber is really big so with a 500 piston it has to have a big dome to get the compression out of it. The xr 500 piston is super heavy and will need a HD rod to stay together. The 350x head can be made to flow just as much or more with a big valve port & flow job done. If that was qa better way to build one I would have built my kits like that. With the way I did it we can run a much lighter flat top piston that helps with the filling of the cylinder while still running a stock rod. That bike was built 20 years ago, if it was the way to go I would still be building that way.

  11. #11
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    Quote Originally Posted by Joseph Farrow View Post
    Hey Harry I have several Dirt Wheels from the late 80's through the mid 90's. I will see if I can find it.
    Also the XR and Ascot head are a little different. The Ascot has wider exhaust ports. I think the bolt on the same.
    I believe the Ascot exhaust ports are a larger diameter but still the same width center to center of each port.
    Last edited by RapidRick; 05-18-2015 at 04:12 PM.

  12. #12
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    "Mickey" thanks for the more in depth explanation between head usage. The XR500, XL and FT heads aren't real common, add to that I think the XR used a reed cage a couple years limits them even more. But given the 500 exhaust valves are bigger than the 350x intake valves one would think more flow. I know not always the case, many variables come into play. If a person already has a good 500 head the expense of installing larger valves and porting the 350x and cost of the mods to install the 500 head is less. Granted I being a manual Machinist makes it seem simple regardless its expensive for the average person to purchase an have a shop machine the cylinder and cases for the larger piston needed.

    So.....did any of the magazines do a project write up of the XR500 (Ascott) head installation? or are we left still thinking it's black magic? rumor?

    Click image for larger version. 

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ID:	216141 Had Aries make this custom 89mm piston to fill the 500 combustion chamber.

    "HJ" Click image for larger version. 

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    ’84 YT60
    ’85 350x (423cc) with ’81 XL500 head conversion
    ’83 XR500 (628cc) converted 3 Wheel hybrid
    ’73 CB750 K3 converted 3 Wheel hybrid
    ’86 TRX250R chassis XR650L engine hybrid
    ’89 TRX250R (stock )
    ’90 LT500 Quadzilla
    ’85 FL350 Odysses ( water cooled head )
    Lost (sold) but not forgotten ’80 ATC 110 (205cc on alcohol ) ’83 200x ( 222cc ) ’83 200x ( 185s eng ) ’85 350x ( stock )
    added to the collection recently, (2) '70 US90 Aquarius Blue and '74 ATC90 Daytona Orange

  13. #13
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    Quote Originally Posted by HairyJR View Post
    "Mickey" thanks for the more in depth explanation between head usage. The XR500, XL and FT heads aren't real common, add to that I think the XR used a reed cage a couple years limits them even more. But given the 500 exhaust valves are bigger than the 350x intake valves one would think more flow. I know not always the case, many variables come into play. If a person already has a good 500 head the expense of installing larger valves and porting the 350x and cost of the mods to install the 500 head is less. Granted I being a manual Machinist makes it seem simple regardless its expensive for the average person to purchase an have a shop machine the cylinder and cases for the larger piston needed.

    So.....did any of the magazines do a project write up of the XR500 (Ascott) head installation? or are we left still thinking it's black magic? rumor?



    Click image for larger version. 

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ID:	216140 Click image for larger version. 

Name:	DSC05366.JPG 
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ID:	216141 Had Aries make this custom 89mm piston to fill the 500 combustion chamber.

    "HJ" Click image for larger version. 

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    All these heads are old school when it was thought the ex. should flow as much as 85% on the intake, it's now more like 65%. So on the 400ex and the 350x I don't run bigger valves, they already flow more then they need to. The 500 heads are bigger stems also so they have to be bigger just to flow as much as they do. The smaller ex. ports work better.

  14. #14
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    Quote Originally Posted by Mickey Dunlap View Post
    The smaller ex. ports work better.
    Because the exhaust is under more pressure and therefore the exhaust gas velocity is greatly increased thus evacuating the chamber more rapidly?
    Have '85 350X-XR500 Hybrid,
    Had Nicholson framed: 90/110, 185s, Gen I 500, Gen II 500
    Had Bandito Framed 90
    Have Vey's Framed 90
    Have too many parts

  15. #15
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    ? I have a xr500 and ascot and stock 350 head if you want to some flow numbers? I would like to see the difference cause like Billy said it's one of those " one of these days projects" that I have laying around. But if it's not going to be worth the time ?and Mickey you are not all that far from me ?
    If its on the internet its got to be true they can't put any lie's on the internet

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