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Thread: Everything Big Bore's triumphant return!

  1. #1
    Join Date
    Nov 2003
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    Everything Big Bore's triumphant return!

    Hey 3ww. Been a little bit. Really nice to see the forums have remained this active through the FaceBook era!

    As some of you may know I've worked closely with Corey Sprock over the years helping him produce products he had designed. We even had a service shop together at one point. He has to a certain degree "retired" from producing aftermarket performance parts for the powersports community. I have been tooling up over the last year to basically carry the torch from here with some of his products. SO, I want to let you guys know I will be releasing a decent amount of new(and old) products this year.

    I have currently been cranking out 310 Big Bore kits for the Tri-Z. I currently have a couple in stock if anyone is interested in purchasing one.

    I will also have some of the other kits, as well as a few new cylinder kits to release this year.

    Anyways wanted to stop in and say hi. I have some images uploading right now. I'll have them posted in a bit.

    Eric
    My feedback: http://www.3wheelerworld.com/showthr...k-for-ATC-Eric

    Survivor! TF: 07, 08, 09, 10, 11, 12, 13 Sandpuppies: 07, 08, 09, 10, 11, 16, 17, 18 Imperial Invasion 09, 10, 11, 13, 15, 16, 17, 18, 19, 20

    Everything Big Bore on FaceBook

  2. #2
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    Nov 2003
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    My feedback: http://www.3wheelerworld.com/showthr...k-for-ATC-Eric

    Survivor! TF: 07, 08, 09, 10, 11, 12, 13 Sandpuppies: 07, 08, 09, 10, 11, 16, 17, 18 Imperial Invasion 09, 10, 11, 13, 15, 16, 17, 18, 19, 20

    Everything Big Bore on FaceBook

  3. #3
    Join Date
    Mar 2010
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    Arizona
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    Please remake his billet cool head for the 1st generation Tecate (but fix the head stay). There are a lot of people who want one.

  4. #4
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    Apr 2014
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    Edmond, KS
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    Yes it has been a while. Thank you for starting to produce more parts for out beloved trikes.

  5. #5
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    Hey guys I actually am working my way towards the 1st gen Tecate heads, among many other items. I'm going to carry a larger presence back here on the forums, so stay tuned.

    A few other things I have for the Tri-Z right now.

    Brand new Head stud kits. Black Onyx high tinsel strength steel.





    I have VForce reeds, and billet intakes in stock.





    I also have T3/T4 billet intakes in stock as well. I will have T3/T4 heads in the near future. I have a number of them ready to go, but don't have o-rings. So I'm going to have to have some custom made before I can sell any.

    Thanks for the support. There's a lot RIGHT around the corner!
    My feedback: http://www.3wheelerworld.com/showthr...k-for-ATC-Eric

    Survivor! TF: 07, 08, 09, 10, 11, 12, 13 Sandpuppies: 07, 08, 09, 10, 11, 16, 17, 18 Imperial Invasion 09, 10, 11, 13, 15, 16, 17, 18, 19, 20

    Everything Big Bore on FaceBook

  6. #6
    Join Date
    Mar 2010
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    Quote Originally Posted by ATC-Eric View Post
    Hey guys I actually am working my way towards the 1st gen Tecate heads, among many other items. I'm going to carry a larger presence back here on the forums, so stay tuned.

    A few other things I have for the Tri-Z right now.

    Brand new Head stud kits. Black Onyx high tinsel strength steel.





    I have VForce reeds, and billet intakes in stock.





    I also have T3/T4 billet intakes in stock as well. I will have T3/T4 heads in the near future. I have a number of them ready to go, but don't have o-rings. So I'm going to have to have some custom made before I can sell any.

    Thanks for the support. There's a lot RIGHT around the corner!
    Is your billet intake for the T4 set at an angle like stock, or does it go straight back?

  7. #7
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    Nov 2003
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    Quote Originally Posted by christph View Post
    Is your billet intake for the T4 set at an angle like stock, or does it go straight back?
    Angled like stock.

    My feedback: http://www.3wheelerworld.com/showthr...k-for-ATC-Eric

    Survivor! TF: 07, 08, 09, 10, 11, 12, 13 Sandpuppies: 07, 08, 09, 10, 11, 16, 17, 18 Imperial Invasion 09, 10, 11, 13, 15, 16, 17, 18, 19, 20

    Everything Big Bore on FaceBook

  8. #8
    Join Date
    Apr 2011
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    Thank you for what you’re doing Eric.

    I stocked up on intake’s and impellers a few years back, so that’s covered. At the moment I’m putting together a power valve engine, so probably not looking for anything you make at the moment.

    However, if your big bore sleeves are blanks I might take one with a piston someday.

    I see you have some head studs, but two of the cylinder studs on the Tri-Z & YZ have been discontinued. Not sure of the market, but I’d take a few if they were available.

    Not trying to goad you into anything (well, yes I am) but there might be a market for an aluminum YZ cylinder intake spacer that points the carb straight back.

    I’m not 100% sure about this as I haven’t set the engine into a frame yet, but there certainly isn’t an option besides running a pod filter, or some complicated plumbing with the YZ cylinder.

    And of course there is the issue of the clutch covers that I recall Cory was looking into. If you decide to pick up that torch there will undoubtedly be a small but steady need for these over the next decade. They hardly ever come up on eBay anymore and if they do it’s 300+. From my experience even the ones that are available on running engines that come up once in a while have started to crack. I thing it’s only a matter of time till they all brake.
    Last edited by El Camexican; 06-24-2020 at 09:03 PM.

  9. #9
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    Nov 2003
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    All good stuff here man. And thank you. I've been dreaming of getting the wheels turning on all this for a long time. The sleeves I use are custom cut, not blanks. BUT I have given a lot of thought to putting my hands on a YZ cylinder to see what can be done. Should be decently cut and dry to get a sleeve lined out. And I know that would open the door to the vintage bike market as well. I know its not a huge market, but at the end of the day I'm not looking to retire on all this. I enjoy building this stuff. I enjoy putting engines together. And I make enough money to make it worth my time. So yeah, I need to find a YZ cylinder. If anyone out there has one they want to loan/give/sell me let me know. I can do some research and see where it goes.

    Head studs. I had these made. They are brand new. M8 x 1.25. Lets just say I have a lot of them lol. So I have advertised them in kits for anyone interested. $20 shipped for a set of 6 to your door. They are 1 mm shorter than the stock stud. I remove material from the cylinder head for the big bore kits, so they work better with the billet heads being just a hair shorter. They still work 110% A Okay with stock heads and cylinders.

    The intakes on the bikes, they have the same bolt pattern as the Tri-Z do they not? So wouldn't the billet intake I have that angles the carb (pictured above) work?

    I still have hopes of doing something with clutch covers. I know what needs to be done, and how to do it. It's simply a matter of putting it into action, and getting the checkbook out. But yes at some point, if not me, someone needs to address it!

    Eric


    Quote Originally Posted by El Camexican View Post
    Thank you for what you’re doing Eric.

    I stocked up on intake’s and impellers a few years back, so that’s covered. At the moment I’m putting together a power valve engine, so probably not looking for anything you make at the moment.

    However, if your big bore sleeves are blanks I might take one with a piston someday.

    I see you have some head studs, but two of the cylinder studs on the Tri-Z & YZ have been discontinued. Not sure of the market, but I’d take a few if they were available.

    Not trying to goad you into anything (well, yes I am) but there might be a market for an aluminum YZ cylinder intake spacer that points the carb straight back.

    I’m not 100% sure about this as I haven’t set the engine into a frame yet, but there certainly isn’t an option besides running a pod filter, or some complicated plumbing with the YZ cylinder.

    And of course there is the issue of the clutch covers that I recall Cory was looking into. If you decide to pick up that torch there will undoubtedly be a small but steady need for these over the next decade. They hardly ever come up on eBay anymore and if they do it’s 300+. From my experience even the ones that are available on running engines that come up once in a while have started to crack. I thing it’s only a matter of time till they all brake.
    My feedback: http://www.3wheelerworld.com/showthr...k-for-ATC-Eric

    Survivor! TF: 07, 08, 09, 10, 11, 12, 13 Sandpuppies: 07, 08, 09, 10, 11, 16, 17, 18 Imperial Invasion 09, 10, 11, 13, 15, 16, 17, 18, 19, 20

    Everything Big Bore on FaceBook

  10. #10
    Join Date
    Mar 2010
    Location
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    Quote Originally Posted by ATC-Eric View Post
    Angled like stock.

    Sweet. How much? Do you get the rubber manifold with it?

  11. #11
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    Nov 2003
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    $125 to your door. Yes they do come with the boot. And I probably should have found one with less finger prints on it for the picture lol.

    Quote Originally Posted by christph View Post
    Sweet. How much? Do you get the rubber manifold with it?
    My feedback: http://www.3wheelerworld.com/showthr...k-for-ATC-Eric

    Survivor! TF: 07, 08, 09, 10, 11, 12, 13 Sandpuppies: 07, 08, 09, 10, 11, 16, 17, 18 Imperial Invasion 09, 10, 11, 13, 15, 16, 17, 18, 19, 20

    Everything Big Bore on FaceBook

  12. #12
    Join Date
    Apr 2011
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    Quote Originally Posted by ATC-Eric View Post
    All good stuff here man. And thank you. I've been dreaming of getting the wheels turning on all this for a long time. The sleeves I use are custom cut, not blanks. BUT I have given a lot of thought to putting my hands on a YZ cylinder to see what can be done. Should be decently cut and dry to get a sleeve lined out. And I know that would open the door to the vintage bike market as well. I know its not a huge market, but at the end of the day I'm not looking to retire on all this. I enjoy building this stuff. I enjoy putting engines together. And I make enough money to make it worth my time. So yeah, I need to find a YZ cylinder. If anyone out there has one they want to loan/give/sell me let me know. I can do some research and see where it goes.

    Head studs. I had these made. They are brand new. M8 x 1.25. Lets just say I have a lot of them lol. So I have advertised them in kits for anyone interested. $20 shipped for a set of 6 to your door. They are 1 mm shorter than the stock stud. I remove material from the cylinder head for the big bore kits, so they work better with the billet heads being just a hair shorter. They still work 110% A Okay with stock heads and cylinders.

    The intakes on the bikes, they have the same bolt pattern as the Tri-Z do they not? So wouldn't the billet intake I have that angles the carb (pictured above) work?

    I still have hopes of doing something with clutch covers. I know what needs to be done, and how to do it. It's simply a matter of putting it into action, and getting the checkbook out. But yes at some point, if not me, someone needs to address it!

    Eric
    You probably know most of this, but for those who might not here goes.

    - To the best of my knowledge the YZ cylinder from 1983 to 1987 bolts to the Tri-Z cases, but the 83 is the only year that the intake points straight back like it does on the Tri-Z. 84 to 87 are angled to the left side of the frame. The 85 cylinder is supposedly the most desirable combination due to the hit and miss power-valve experiments Yamaha was doing at the time.
    - None of the YZ cylinders will accept a Tri-Z intake. Four bolts VS six and a much larger cage and boot on the YZ. I don’t think the bikes used the boost bottle after 82.
    - Bad news is that you would likely need a different sleeve for each year of YZ cylinder unless you get blanks and cut the ports yourself. That said Kustom Kraft got someone to make me a custom Tri-Z sleeve with a bridged exhaust port a couple years back for the standard price. Maybe it was LA Sleeve? I just had to wait a few months for it. There is another respected builder in CA whose name I won’t drop here that makes a 72mm bore YZ sleeve with multiple over-bores as well. Regardless of what bore you end up going with the power vale probably needs to be cut on anything larger than 70mm.
    - The pistons are different as well. The Tri-Z has two small windows on the intake side and the YZ has a half moon cutout and no windows. The YZ piston is also taller by a few thousandths of an inch. This is because the YZ cylinder is taller that the Tri-Z’s for some reason. Adding a YZ piston to a Tri-Z will raise your compression, but if you’ve cut your head you’d best check your clearances when putting in a YZ piston.
    - The transfer port tracts and windows on the 85 YZ are considerably different than the Tri-Z.
    - The boyesen, or boost port on the 85 YZ cylinder is on the right-hand side of the cylinder. From what I’ve read the “trick” mod back in the day was to punch a ½” round hole on the left side and NOT try to match the shape of the stock port, but because of the angle of the intake tract there’s even less material to add the port on the YZ than there is on the Tri-Z where the famously can crack. I’m on the fence about trying, good cylinders are as hard to come by as the Tri-Z's.

    Re- Clutch covers. I’m thinking of getting one machined flat right across the indented “Yamaha” and then welding on a 3/16” or .250” aluminum disc. I don’t know if this will help in all scenarios as I’m convinced that there are over half a dozen ways to break the cover. In no particular order:

    1 – Let the “Clip” P/N 90468-26048-00 on the kicker shaft get worn and allow the idler gear of a running engine to make contact with the starter gear that should have retracted on the worm shaft, but didn’t because the clip is worn resulting in a catastrophic failure.
    2 – Positioning the kick start lever too far back (counterclockwise looking from the right side) onto the splined shaft. When you do this it means that you’re over-rotating the kick start assembly before it stops on the foot peg and stressing the cover. It also exacerbates the next issue.
    3 – Bent RH foot peg. This allows the started to over-rotate just like in the example above, but if you combine the two scenarios, or rotate the kicker clean past the foot peg you will eventually crack the cover between the shaft housing and the Yamaha badge.
    4 – Forgetting to put all the parts back together. There is a thin washer, 90201-13205-00 that is discontinued. Based on the engines I have and the multiple others I’ve torn down it would seem that 80% of “mechanics” don’t put this washer back into the assembly’s.
    5 – Locating dowels are missing. This goes for the kick plate and the clutch cover. On lots of engines they are there just to align gaskets, but on the Tri-Z they are integral components needed to keep the gears lined up and somewhat supported. Again, it seems there are few used engines out there with all the dowels installed.
    6- P/N 90468-26048-00 rusted to the kicker gear. Only seen this once, but whoever decided that he could bust it loose with his foot cracked the tab that holds the loop on the clip and then RH engine case to crack inside that D shaped recess it sit in just below the clip holder. Amazingly the clutch cover on that engine was still good.
    7 – High compression. Maybe not in all cases, but it doesn’t help. My Tri-Z registers over 200psi and my cover is still the original, but if any of the other issues mentioned were not address I have no doubt it would crack in short order.
    8 – Kicking the engine over haphazardly. Stop and think before each kick. Kicking it over wildly is asking for trouble. Make sure your foot is pointed straight forward and pre-engage the gears before you apply full force. Shortening the stroke of your kick a little will help prolong the life of the start lever and foot peg as well. It sucks that we have to pay so much attention to this, especially when you’re having trouble getting one fired up, but if you want the cover to last you need to respect the fact that it’s a very delicate assembly.
    9 – The design sucks!!! The aluminum is thin, the engineering screams “Lets make a forward kicker that fits YZ cases as cheaply as possible”. There seems to be no margin of safety built into these things and to top it off they made them out of crappy material and then discontinued the cover after the standard 10 years. We are at the mercy of the sellers now, so lI really hope you can come up with something.

    This is the cheapest cylinder on eBay at the moment. There is also a guy in Sweden selling a complete cylinder for $220 with the power valve. It's a good price. https://www.ebay.com/itm/1985-YZ250-...QAAOSwhIZbAyEZ

  13. #13
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    Nov 2003
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    Killer stuff man! Lot of good info on the yz I didn't know. Lot of guys over the years have played with the power valve motors in the Z, but I never crossed that bridge.

    I'm going to slowly try to put my hands on an 83. We will see.
    My feedback: http://www.3wheelerworld.com/showthr...k-for-ATC-Eric

    Survivor! TF: 07, 08, 09, 10, 11, 12, 13 Sandpuppies: 07, 08, 09, 10, 11, 16, 17, 18 Imperial Invasion 09, 10, 11, 13, 15, 16, 17, 18, 19, 20

    Everything Big Bore on FaceBook

  14. #14
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    Good to see you again Eric..... Great post too

    I'm pretty stoked about your new/renewed venture. I have an 85 T3 in the paddock now torn down and awaiting a total rebuild so I will be hitting you up soon for some Kawi Love

  15. #15
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    Quote Originally Posted by ironchop View Post
    Good to see you again Eric..... Great post too

    I'm pretty stoked about your new/renewed venture. I have an 85 T3 in the paddock now torn down and awaiting a total rebuild so I will be hitting you up soon for some Kawi Love
    Hell yeah man been a while. Like I said its cool there's a good amount of traffic still here. Might just make myself at home (again lol)
    My feedback: http://www.3wheelerworld.com/showthr...k-for-ATC-Eric

    Survivor! TF: 07, 08, 09, 10, 11, 12, 13 Sandpuppies: 07, 08, 09, 10, 11, 16, 17, 18 Imperial Invasion 09, 10, 11, 13, 15, 16, 17, 18, 19, 20

    Everything Big Bore on FaceBook

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