Truenotch

Hopefully you get it sorted . You'll be able to take it easy and do 11s without breaking anything......

Woohoo! Welcome to the cave of small bikes. You might never escape.

I reckon 3 support vehicles will be good. F150 sounds like it would make a sweet ambulance too.

Wof, license, helmet, regular riding gear.

Correct. Helmet, shoes, not much else (people race in a T shirt and shorts).

Gave the carb a good clean with @Geophy's ultrasonic cleaner today. Blew out all the jets and passages and re-assembled it with the standard 17.5 pilot jet. Whacked it all back together and the hang + pipe bangs were exactly the same. Then I wound the idle screw out as far as I could so it wouldn't idle and it sounds good: Maybe the pipe bangs are a normal characteristic for these motors when the idle is cranked up a bit? Took it for a hoon and adjusted the mixture screw a bit. It goes really well! I might have been chasing a red herring by looking for a lean issue with the carb, but at least now I know it has a very clean carb, new crank seals, correct oiling (premix). Next job is to gear it up .

@Beaver @mark105 @Geophy @Archetype @Yowzer @Zeubin @macabre @bobby1930 @vk327 You guys keen for caffeine and gasoline, or shall we do the Raglan run again?

@peteretep - it’s a little pump that runs off the primary reduction gear / main clutch gear and it’s operated by the throttle via a split cable. As you wind the throttle on it opens the pump more and you can set the min/max position of the pump. The pumps can wear our and get weak, which I suspect has happened here. I’ll probably rebuild it later on for ease of use. I tested mine by pulling the hose off and idling the bike with the pump turned to max and it gave a dribble so I figured it was good. The proper way is to set the RPM and measure how much comes out (which I didn’t do because no tacho).

I’ve got a 17.5 from my spare carb if you want to have a play?

Fuel can, panini storage, tank bag and hypercolour handlebar bag fitted. The rack is from the FS1: I’ll need a backpack for undies and Brian Lowns too.

Forgot to add: Current sprockets are 14/48 (3.429:1) Desired sprockets are: 14/39 (2.786:1) 18.75% increase in gearing and means I might actually use the lower gears on the open road.

I've been chasing the cause of the seize since last weekend and have done a couple of things. The bike acts lean on the overrun, which is usually caused by a vacuum leak or a lean pilot circuit in the carb, so I've been through a few things in search of the lean hang. Replaced both crank seals - no change Set float level in the carb - no change Changed the reeds over (they weren't seating completely flat on the block) Changed 17.5 pilot jet to a 30 from another carb - it's now very rich up to 1/4 throttle, but still hangs and pops on the overrun Refitted air box properly (it was loose when it seized and could have been leaning the mixture) - still hangs Disconnected the oil pump and changed to premix I highly recommend Blackwood Yamaha in Cambridge for Yamaha parts. They were super quick to respond to my queries and I had my crank seals on the same day. Their prices are reasonable too. I took it for a hoon yesterday after work and it didn't seize, so that's a bonus. I'm using the old rattly cylinder for testing so I don't have to care if it seizes again. It went pretty well and cruised happily enough at 70-75k, but felt like I was wringing its neck at 80+. When it seized last weekend, I was doing 85kph, so I must have been pulling a few revs! It's hard to find information about the MX100, but the specs I've found online for the older DT100s say that the max power RPM is 7500 (pre 1980 DT100s have the same engine but with points instead of CDI). I did a few calculations to see what revs I was pulling at 85kph: (Black is standard gearing, red is my new planned sprocket size) At 85kph I would have been doing around 8300rpm! This is probably a bit hard on an old engine that's only designed for 7500-8000 max. The red numbers in the table show the RPM for the rear sprocket I want to fit - this will sit me at about 6700 at 85kph which is a much more manageable number! It will also allow me to wind it out to higher speeds when I need to. Here's a link to the wheel speed/RPM calculator I used: http://woodsware.aciwebs.com/gears/ I'm not convinced that the problem is fixed yet, but it's looking promising. I'll head to @Geophy's place on Sunday to use his ultrasonic cleaner to make sure the pilot circuit is nice and clean. Here's my list of what might have been the problem: Lack of lubrication resulting in high cylinder temps (trusting the original oil pump) Too many RPMs Air box boot not fitted properly - LEAN Partially blocked pilot circuit - LEAN Piston to cylinder clearance too tight on new cylinder Ring gap not set correctly All of the above I'll get the new cylinder back onto it and will go for another hoon and see what happens. It's under 2 weeks until the big ride, so the pressure is on!

Are these the springs you're using? Their website says they are progressive to soak up bumps etc, which might mean that you'll get extra droop when compared to a linear 4.7kg/mm spring. https://shop.battlegarage-rs.com/products/bgrs-x-swift-ae86-springs-rear-coilover-type

While I get the point about rates here, adding droop with keeper springs is still useful. It stops cars from picking up inside wheels around corners and keeps wheels on the ground over big dips and bumps. @Bling - are the springs you’re using on an adjustable perch, or are they at a set height? If you can’t fit keepers and don’t get enough droop then adding weight at cert time is the only option (full tank of gas, couple of duffel bags full of concrete etc).

Hey, that's sweet as. No need for any special paperwork. I'll make a note of it.

You can't delete your comments... But you should be able to edit it. Too late though. Beware of the Taniwha.

Don't lie. We all you know you've got their complete works stashed in your phone at all times.

You know me so well.

Carpe diem: seize the day. I blarped around town all morning yesterday - the bike is fun! Tried to ride it out of town with @Beaver and got about 1km at 85kph, then it locked up. It’s had quite a bit of lean-hang and I probably should have looked into it more.... I suspect the left hand crank seal is the cause. Pulled the flywheel and stator plate off and you can see evidence of oil that’s made its way out. I’m going to throw some crank seals at it this week, clean up the piston / barrel and hope for the best. 2 stroke 4 lyfe.

We used to do Rose & Crown back in the day. It worked well.

I’m f we do Raglan again, we should do it differently. Was chatting to Tank and he suggested parking at the domain and buying fish n chips from that little stall in the park. If we do Caffeine, we could invite the Auckland crew to join in?

Took the FS1 for hoon with the Speedcocks after work. Good practice for Te Urewera, but it would have been nice to be on the MX! When I got home I was inspired to work on the MX. First up, I took a video of the rattle that I suspected to be caused by piston slap: The camera did a good job of picking up the sound. It didn’t sound this bad IRL. I had a re-bored and oversized barrel/piston on rev other MX, so pulled that off and swapped them over. Here’s what it sounds like now: Much better! It has a bit of lean-hang going on, so I’ll pull the carb apart, clean it and check the jet sizes before a shakedown on @mark105‘s paddock this weekend. Here’s a pic of it looking more complete for good measure:

I've moved this thread to the 2 wheels section for you (more appropriate fit). Damn this is cool! I love the discreet electric conversion.

New front tyre fitted: Speedo in place: Dodgy epoxy job to keep the sensor where it should be. I slapped a couple of neodymium magnets onto it for a stronger signal: And this sweet accessory courtesy of @Geophy. Perfect for a few beers and other paraphernalia.