Introduction and YZ250 swap

Discussion in 'Engine Mods and Swaps' started by HannsGruber, Nov 5, 2017.

  1. HannsGruber

    HannsGruber Member

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    Hello! I'm HannsGruber.

    Since I'm doing this swap I thought I'd post what pictures I have here and answer any questions I've discovered to some potential frequent problems as I've come across and solved them. I didn't intend to log the build, so the pictures I have are more milestone-y that I've taken along the way to show friends and family. I can take more detailed current pictures of anything anyone needs.

    Backstory
    I had an opportunity to buy this quad from a friends elderly parents. They had originally purchased the quad new for their grandchildren in 1997. Sometime in the past 1.5 years or so the grandchildren (adults) ran it with straight gas and burned hole through the piston.

    After some discussion one night at dinner I agreed to go look at it, noticed the lack of any compression and made an offer. $500 later I had a quad, title, and a full set of nearly new desert paddle tires (front and rear).

    Here's the blaster as it arrived in my garage (pardon the mess)
    [​IMG]

    I immediately tore into the engine...
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    and found this mess
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    Metal. Metal everywhere. It puked metal everywhere, bottom end, intake, exhaust. The reeds were essentially sandblasted with it.

    A quick trip to the internet and I had ordered everything I needed to get it running again. Piston, cylinder, reeds, clutch. Carb was cleaned.

    [​IMG]

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    I took the opportunity to upgrade the reeds to VForce 4's

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    (Not pictured, but I took the engine out to flush the bottom end. There was no discernible play in the crank that would indicate wear. Somehow the bottom end survived.)


    All back together
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    I took it out to the local OHV park and put maybe 30 miles on it that day.
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    Ran so smooth, great power. But only off the line. It was also extremely tip happy and the stock suspension was starting to take its tole on my body. I'm not a small guy, I'm 6' 1", and while I understand there's larger quads that can be bought, It's never been my prerogative to just *buy* what works. Obviously, I bought this mess.

    A swap is in order.

    (continued in my next reply)
     
  2. HannsGruber

    HannsGruber Member

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    Continued from OP


    Current Situation
    At this point in time I've sorted out many of the issues most people have with these swaps.

    Engine

    The first issue is finding an engine. I scoured ebay and craigslist. There was either complete junk or expensive clean completes for $1500. Luckily one day a listing on ebay popped up for a clean, running, 1998 YZ250 engine, which I bought.

    The engine install was pretty straight forward.

    Swing arm
    The blaster has a narrower swing arm mount than the YZ250, so a small modification to the swing arm is needed.

    Here's the installed YZ250 engine at the swing arm (spoiler alert)
    [​IMG]

    The right hand inner side with the bushing/cap is where the modification is needed. I can't remember the length, but a piece no bigger than an inch or slightly less needs to be removed, and then there's a smaller metal bushing that needs to be cut to length inside as well. Other builders disregard that outer bushing/cap. I don't know why. Account for it in your measurements and it'll fit right back on -- and look factory.

    Engine Mounts
    Let me preface by saying me and welding thin wall tubing don't mix. It's not for lack of trying, it's just that my welder doesn't have the fine voltage controls I need to not sometimes just blast through. Now that that's out of the way...


    The first step to mounting this thing is to cut off the factory blaster mounts as close to the frame as possible and save them. I reused mine for the front mounts and built a bracket that I welded on for the bottom engine mounts.

    [​IMG]
    [​IMG]

    Notice how great the intake and carb boot line up?

    Stance and Rear Suspension
    Two of the biggest complaints I had. The rear suspension, and the narrow footprint. I had a choice in how I solved the footprint issue. I could install wider A-arms, or I could install the widening brackets that simply relocate the mounting points. I decided to buy the relocation kit. If it doesn't work out in the long run I'll buy wider a-arms.

    The kit bolts to the factory mounts and offers new locations to bolt the factory a-arms. This is a +6 kit, so 3 inches wider on each side.
    [​IMG]
    (note the black brackets, that's the kit)

    Rear Suspension (No pictures, visible in others though)
    400ex rear shock swap with the Ken Oconnor bushings. Two way adjustable (compression and rebound).

    Carburetor and Air Filter Connection
    Carb was bought new, Keihin air striker. I wanted to preserve the factory air box so I trimmed the factory air box outlet back, installed a PVC tube, a rubber flared coupler, and it mounted right up.
    [​IMG]
    [​IMG]
    I will eventually cut off that factory blaster intake hanger that's rubbing on the new adapter.

    Next up... The Exhaust Pipe.
     
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  3. HannsGruber

    HannsGruber Member

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    Continued from prior...

    The Exhaust Pipe
    The single biggest obstacle to this entire swap. I've watched all the youtube videos. I've seen people cut every weld and rotate, I've seen them do weird notch cuts for bending and oh my god they all look terrible. I thought there HAD to be a way to get a stock pipe to fit with as LITTLE modification as possible. And sure as heck, there is.

    Step 1.) Acquire a pipe. This is not the right pipe. This is a $200 mistake. Anyone need a pipe for a 1999+ YZ250? I've got one that doesn't fit my 1998 engine :D

    It will however work for me to describe the method for installation.

    Step 2.) Make a purchase of a 1.75" OD VBand clamp. I bought the Vibrant brand, but you can use whatever.

    Step 3 Optional.) Buy a pipe expander

    Step 4.) Return the pipe expander because it was harbor freight and exploded. Seriously, don't buy their pipe expanders, they will explode.
    [​IMG]


    Start off by taking your pipe and cutting the end off that runs out to the muffler.
    [​IMG]

    Now cut the flange off (in my case a boss, but like I said, this is the wrong pipe) here, this is where you'll install your vband clamp.
    [​IMG]

    Why a VBand clamp? Well, first to install the pipe you take the seat off and gas tank out. With the exhaust end cut off you insert the pipe up through the frame rail and slide the flange end in through the lower front frame rails. It will fit, but only JUST. Once it slides through, you rotate it down.

    [​IMG]

    Some bad photoshop details.

    [​IMG]

    That gets you 95% of the way there. Now you'll find that your pipe to engine connection is about 3/4 of an inch too far away. This is because in a dirt bike application the frame rails straddle the engine, but in the blaster, the frame rails are further forward in front of the exhaust. The vband clamp gives you that extra 3/4 of an inch you need PLUS makes it removable. If you weld in 3/4 of an inch of pipe where I show you it will NOT fit.

    The pipe expander mentioned earlier is to help the vband clamp slide into the exhaust pipe. A lap joint is a stronger than a butt joint, but in my case I was forced to use a butt joint when welding the vband clamp flanges on.

    When all is said and done the pipe will be in and you will have only made two cuts.
    [​IMG]
    [​IMG]
    [​IMG]

    The silencer mounts right up and with the removal of a small section of pipe, mounts back up to the new YZ250 pipe. Clean, baby. Clean.

    [​IMG]

    Next up, the cooling system...
     
    Last edited: Nov 6, 2017
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  4. HannsGruber

    HannsGruber Member

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    Continued from prior...

    The Cooling System

    I considered a bunch of mounting options for a radiator for a while before settling on a design idea I liked.

    I love the look of a banshee with it's high and proud radiator, and I decided to pay homage to that with a very custom mounting and protection solution.

    The radiator I chose is a radiator for a 01-05 Raptor 660.
    [​IMG]
    (Shout out to Mighty Car Mods)


    I had to fabricate a lower mount to accept the pin on the bottom of the radiator. These radiators only bolt in two places, with the bottom secured with said pin.
    [​IMG]

    Test fitting into the lower bracket
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    For the top mounts I fabricated a bracket that I welded to the front frame. It has two captive nuts and grade 8 hardware to secure the radiator in place at the right angle. It fits nicely under the front cowl.

    [​IMG]
    [​IMG]

    Radiator mounted
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    [​IMG]

    This is exactly the look I wanted. It's like a little brother to a banshee.
    [​IMG]

    Now obviously that radiator is in a dangerous, dangerous spot. I wanted a tough cover that would let a lot of airflow in but deflect most anything that hit it. So I went to sketchup and designed a protective grill.

    [​IMG]
    [​IMG]
    1/8" steel spec'd. My radiator will deflect small arms fire, LOL

    Steel cut, welded. In progress pic
    [​IMG]
    (yes I realize I misspelled vertical 6 times.)

    And before anyone asks, I have to weld outside, so flux core is all I can use since my area is VERY windy. Any shielding gas I use will blow away. So splatter is what I deal with. I could grind it off but who cares.

    Mounted up. It uses the same mounting points as the radiator for ease of installation.

    [​IMG]
    [​IMG]
     
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  5. HannsGruber

    HannsGruber Member

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    And this is where I'm at with the project. All I have left to do is finish routing the coolant lines, put a wider rear axle in to match the new widened front, and weld a few gussets in. I'll be detailing those activities as they progress, hopefully within the next week or so this thing will be ready to go, go, go!
     
    Last edited: Nov 6, 2017
  6. speedyslyder

    speedyslyder 2 STROKES RULE Technician

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    WOW!
    welcome to the forum awesome job:)
     
  7. HannsGruber

    HannsGruber Member

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    Hello, and thanks! Its been good fun reading about all the other builds here.
     
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  8. HannsGruber

    HannsGruber Member

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    Update for tonight. Added expanded metal to the back of the grill to prevent debris from being redirected into the radiator, and cleaned off the spatter. Looks great now.

    [​IMG]
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    I also got the coil mounted, coolant lines run and chain installed.

    [​IMG]
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    [​IMG]


    Home stretch!
     
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  9. HannsGruber

    HannsGruber Member

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    Got my kickstarter today and it fit without any modifications what-so-ever. Sweet. Also got a new Protaper handlebar pad just because.

    So the ebay engine runs but the ebay carb is jetted way...way wrong. 55 pilot, 175 main, clip is, well, not sure. Nothing in it is labeled. If you're familier with those china carbs you won't be surprised. I've got a whole new set of jets and needles on the way to throw in it so I can dial the carb in. Hopefully in the next couple weeks I can get it out to the desert for a good test-n-tune.
     
  10. HannsGruber

    HannsGruber Member

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    Disaster!

    Was doing tuning work and somehow managed to shear my woodruff key off and managed to strip out the threads on the crankshaft.

    However, i was able to turn down the diameter of the thread shaft and cut new threads at a 3/8-16 thread pitch (no metric tap and die set on hand). So that disaster is avoided. Pulled the head and cylinder and the cylinder looks great, still has a crosshatch visible, so I've ordered a top end kit with a forged wiesco piston.

    Tuning this is turning out to be a real pain in the butt. But i'll get there.
     
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  11. HannsGruber

    HannsGruber Member

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    Recovery!

    New top end was installed, along with a new clutch side crank seal. No play in either crank bearing was able to be detected. The repair to the crank with the new threads has been a complete success as well.

    I ended up tossing that ebay carb into a box and buying a new used 98 YZ250 carb. Out of the box, gone through, and the quad runs great.

    Had an opportunity yesterday to take it out to the desert and.. oh. my. god. It is FAST. I drag raced a raptor 700, and a raptor 660, and spanked them both while the front end lifted at 150 feet. Multiple times. And that's with two bald tires. I never got a chance to put on the paddles, the sand was too full of rocks. Next weekend I'm headed to Glamis or Gordons Well so I'll take some video for you all.

    So it needs a longer swingarm and the wider axle, absolutely. Otherwise, I'd say this build is done. I am so, utterly pleased with how it's running. Got a solid full day on it, never fouled a plug. It's a tad bit rich but that's okay since it's a sand machine.

    [​IMG]
     
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  12. Awk08

    Awk08 Moderator Staff Member Technician Forum Supporter

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    Nice work Hanns.
    Keep the ride reports coming
     
  13. Markblaster

    Markblaster Custom blaster

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  14. HannsGruber

    HannsGruber Member

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    Hey all, it's a couple days post desert trip. Got there late, did a night run, quad ran good. Needs more gearing to handle the increased load from the sand, but it sheared the bolt again. No repairing that this time so I'm going to put a crank in it. No big deal, I knew it needed one, was just hoping the band-aid would last.

    Took my dirt bike out in place of the quad (always have a backup) and crashed hard late the next day. Went down a dune, didn't notice the hill on the other side was a razorback. Launched about 30 feet, landed, compressed the front suspension, head impacted the handlebars, bike rebounded, threw me off, and onto my back. I've got a sprained ankle, bruised eye socket, a fat lip, and a sore back. Always wear your full protection. Nothing broken, thankfully, so I'll be good to go for our christmas trip to the same place LOL

    [​IMG]
     
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  15. speedyslyder

    speedyslyder 2 STROKES RULE Technician

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    ouch
    how is the bike:)
     
  16. HannsGruber

    HannsGruber Member

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    The bike was unharmed. I managed to get it back to camp after recovering my brain marbles for a few minutes. Thankfully the full breadth of the pain didn't set in until AFTER I got back to camp. I kickstarted it on my bad ankle...
     
  17. YZ Otis

    YZ Otis Member

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    Nice work .. be interested in what sprocket set you settle on .. zips along pretty good in 1st at idle, eh.
     

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