Dr. Shop Teacher's Tonic le Moto--Broncco T-XL

Working on engine details: The cylinder head came first. I had cleaned it with paint stripper some weeks ago, and I knew I had to true the head as there was a gasket leak on the exhaust side. You can see the discoloration in the thumbnail below.
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So I used a flat plate with 150 wet/dry to start to true the surface. The first pic shows about a minute in, and the second is when I got it true for the gasket to seat properly. I didn't take a lot off as I wasn't looking for more compression....just enough to get the mating surface flat.
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I cleaned up the head bolts and used anti seize to make sure they didn't bind up in the freshly chased bolt locations. IMG_0559.jpg
Following the torque pattern, I fitted the head in place at 140 in-lbs. I went up in 20# increments.
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I double checked valve lash and it was in spec, so I went ahead and put the valve spring cover on and tightened it down snugly.
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I lapped the flywheel to the crank next. Didn't take much and I cleaned the surfaces with brake cleaner. I picked up a new jam nut and used the Beville washer provided by ARC.
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I have several keys to work with but since the flywheel is already set at 30 degrees, I went with a stock key first.
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I torqued the flywheel to spec at 65lbs.
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Next up was the new coil. I'm not looking to run this engine super hard, so I went with a stock coil as opposed to a PVL. The stock coil will take me to 5000 rpm before breaking up. The air gap is et at 0.030" and I had a feeler gauge in that thickness, but I had to clamp the coil down as the gauge was so stiff.
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I pulled the bolts on the side cover and sealed them with red Loctitie. The side cover is torqued to 140 in-lbs but there is no torque pattern, so I created one. I brought each bolt up from 20 in-lbs at a time.
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I next installed the recoil on the shroud. I didn't have it powder coated as I caught you-know-what on last year's build off bike. I think I'll leave it satin black as the block will be painted satin black also. The shroud extension will be painted black, too.
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Hopefully, we can test fire on Thursday. My sister-in-law's memorial service is tomorrow, so off to Southside VA in the morning.
 
A little bit of work: Waiting on new jets for the Chi-kuni and a new recoil as the one I had exploded, so the engine is going to have to wait. I had some time yesterday to locate and drill the hole for the 2 qt. kart tank through the shroud.
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Today i worked on the disc brake assembly. I disassembled and stripped the paint off the caliper first. then I polished them a bit with a wire wheel and clear coated pieces.
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I needed to make some final adjustments for fitment on the sprocket.
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The sprocket was cleaned up with an oscillating sander and clear coated (knowing I'm going to wear it off at the caliper). I attached it using blue Loctite on the bolts.
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I then test fitted the caliper bracket and had to make still more adjustments to the caliper.
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Mounted on the bike. I need to swap spacers on the caliper side to allow for more side to side adjustment using the two spring loaded screws. No more than a 1/8" difference to get it to grab the sprocket evenly.
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Quasi-Raptor is finally alive! I caught h#ll getting this thing running. I cracked the case open four times over the past week. First to check the Dyno cam timing (off by one tooth), second to adjust the crank seal to stop oil leaking (didn't work), third to replace the Dyno cam with the stock cam after blowing up the starter and stretching the tendons in my right arm (ouch!!!!) and finally, to true the side cover and replace the gasket and the oil seal to stop the oil leak(s). Even with the stock cam, this engine has to be on the compression stroke to start or it will kick big time (not nearly as bad as the Dyno). Once running, I worked a bit on adjusting the carb but I'm sure I'm going to have to go to a genuine Mikuni. Idle is bumpy and still high. It does rev freely and is running pretty neutral to lean. I have to admit I was anxious about building a non-governed engine. Here's a short video:
 
Sweating the small stuff: Got the bearings for the jackshaft mounted and cut the shaft to length. I was sweating the installation because there is no F/R adjustment but everything fit just fine.
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I had removed the cable stop tab on the brake caliper to fit the caliper into place. After measuring and test fitting a bunch of times, I located the cable stop just forward of the top tension screw. This required cutting a new groove in the cable stop for the E-clip as there was too much play.
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I swapped out a couple of nuts, reinstalled the rear wheel and installed the drive chain--I'm going 6:1 from the jackshaft sprocket to the drive sprocket, and will adjust gearing at the input on the jackshaft. I've got about 1" of front to rear adjustment on the rear. The @mrpat chain tensioners worked perfectly.
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Seat mount: I needed to properly locate the seat before moving onto the fuel tank shroud. It was straightforward but I made the bolt holes in the frame a little large to have some adjustment.
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Drive system: I fiddled with the engine location on the motor plate. I had anticipated the input sprocket for the jackshaft would need to located outboard, but it turns out I have enough clearance to mount it inboard. This pic shows the engine mounted on the right set of bolt holes (there are 8 on this plate). This put the engine shroud well over the right side of the frame and would interfere with a foot place on the peg.
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Another view (engine mounted to the right).
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And no, I'm not reusing that old clutch...it was the first one I put my hands on ;)

It finally dawned on me to flip the direction of the flange on the input sprocket. This allowed for the left set of slots to be used to mount the engine. Engine moved over, clearance for my 13 inch long foot and problem solved. I'll need to use a very thin shim between the bearing and the clutch (I have a few left over from last year's build off).

I had an aluminum clutch guard bracket that didn't quite work for an OG Gilson guard for my Trailbike, so I used it for this bike. Will work perfectly. The engine presently sits fully forward, so the guard will cover a bit more of the jackshaft. IMG_0610.jpg That's not the exhaust system I'm going to use (it's actually a big block Tecumseh header courtesy of @David wulf. I broke down and ordered a real Mikuni, so I want to double check clearances before I talk to Robertsons.
 

Attachments

If at first you don't succeed...waste more metal! I had fits over the last two days making things look right. I was able to install the fuel supply to the tank and I worried it would leak---I used a 3/8" brass lamp nut inside the tank and made a rubber gasket for the petcock. No leaks after sitting full of fuel for the day.
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If you noticed, the hole in the tank shroud was off center as the hole saw walked when I was drilling it plus it was just too big. My second thought (Plan B) was to fill the hole with a round and weld it with aluminum....I could not get the heat even enough and this didn't work.
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Then I went back to plan A and decided to cut a piece of aluminum in the shape of a tear drop and drill a hole of the correct diameter (hopefully centered). I made it up and the more I thought about it, the less I liked the look.
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So we went to plan C and re did it more in the shape of the tank and continuing the round cut outs as in the front frame gusset.
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This looked a lot nicer.
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I cleaned up the bracket for the clutch guard and got it ready for sanding.
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Finally, I carried the round cut outs to the tail of the clutch guard.
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I74

Well-Known Member
Nice work ! Love the purple !!
FYI,,
When I used to moonlight in small engine shops back in the day,, we used to cut micro fish films in strips, then stack & staple them together on one end, for setting air gaps. ;)
 
Throwing in the white towel: The Broncco T-XL won't be finished by the deadline. This bike is dedicated to Richard Pearl (@control4userguy), who passed away in December 2018 from pancreatic cancer--leaving a wife and young children. Rich became a good forum friend and those of you who followed his Gilson builds know he was painstakingly precise in all that he did. Rich's death hit home, hard.

In December 2018, I was diagnosed with prostate cancer and have undergone a multitude of tests since then which, of course, have occupied many days. Luckily, it has not spread beyond the prostate and is treatable. I see the radiation oncologist tomorrow to get my tattoos and be mapped for radiation therapy followed by radioactive seeds in late August. If you haven't had regular prostate exams--DO SO.

My mom also has been ill much of the new year and I've had to make many trips to address her medical needs. Life sometimes hits hard at the most inopportune times.

I need to thank @mrpat for his help with the chain tensioners, @CarPlayLB for behind the scenes moral support, @Havasu Dave for behind the scenes moral support, @manchester1 for the awesome seat, and @Harleys Papa for the fenders. I'm sure I missed thanking a fellow minibiker and I apologize in advance. John Jewell Architectural Metals did the welding, the Restoration Shop machined the new rear sprocket, Advanced Coating Solutions did the powder coating. ARC racing provided great technical support as did Dyno Cams. To all of you who added comments and sent suggestions--thanks! The bike will be cool....I just need to be patient.

Below is a video of the engine running with the new Mikuni.

Several problems popped up at the last minute making finishing impossible. Rather than try to thrash the bike together (and make mistakes), I decided to use my time wisely and have it ready for Windber. I had a problem with the brake cable being 3" too short and the throttle cable not working correctly both requiring new cables to be ordered which won't be here in time. I found an air leak in the intake that needed to be epoxied and I had to order new jets for the Mikuni (which took a couple hours of searching for at jetsrus--always measure thread diameter and length and follow their instructions).
 
Hey, at least Eric talks to you. ;) Keep messing with it, I wont move your thread to the Projects section until after the build off anyway....just in case you have one of those days where you get up at 2:30 AM, and suddenly find yourself in this groove where you just can't go wrong prior to May 31st.
 
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