Cannonballs Back Into It With A BT 80

curtisfox said:

How you going to knit a starter?..........................LOL.....Curt

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3d knitting needles!

Yeah may go thru my weedeater junk box and see if a transplant is possible. Good idea Scratch!

So out of desperation to ride I re-engineered the recoil. Took the plastic starter pawl drilled, tapped and installed a small machine screw. Then ground the head square to engage the cranks cup properly. And it works! For a while I guess.

Got several rides in and this is a great little engine(so far). Starts easy(good thing!), idles very well and has a good fat power band. Clutch engages early and pulls easily from standing. I got my ratio for the 24" wheel just right.

I haven't wrung it out as its breaking in but I did briefly do a bit of high speed running and its very smooth. Almost vibe less. What little there is seems to be of a lower frequency than the vibes of a CG and not overly objectionable.

The exhaust seemed quite restrictive as a good bit of induction noise was evident. I removed the end cap of the muffler and shortened the exit tube even with the cap. That solved the problem and it is still very reasonable on sound.
Excepting the recoil issue(not a problem if going electric) I'm very pleased with the engine so far. Still early in the relationship though!

Heres a few pics of the rough out. Not real pretty. Its basically just thrown together to get the engine running and evaluated.

You can see the threaded spring anchors nut on the recoil housing. Breaking in on 25:1. Manual called for 20:1--no way. Its barfing out all manner of black oil as it is. Surprised it runs as well as it does. I run marine fuel with no ethanol. Everything runs better on it.

Nah, no pipe. Will be leaving it as stock as possible.

This build is not very inspiring to me. The frame is better than I expected. The front end sucks big time. Hope to replace it with a MTB suspension fork I have.

Other than the front end the bike runs and rides well. What I hope to wind up with is a reliable, good running beater type bike. One I can use for running errands around the local area. Will paint it and make it presentable. But that's about it. I just want it to work.

I have the Villiers and the B&S builds to lavish some attention too. Need to get back on them.

Got a response from Bikeberry requesting pics and an explanation of what failed. That's reasonable. So far my "fix" is working fine. Has lasted longer than the original recoil.

Scratch the electric start is looking better right about now. I can use an old Snapper mower push start switch. Its HD enough to run the starter directly eliminating the solenoid and wiring. Coupled with a 4cell Lipo its simple and compact. Might do it. Takes all of 20min to reinstall the starter system.

Curt
There are many versions of the Monark springer. some good some not.
This one was made for this frame. It is a 1 1/8 threadless stem. The issue besides needing to be bushed on the rockers is that apparently the stem is turned slightly undersized. The spring mount which also sets the bearing preload/play will not tighten down on the stem. I have drilled the original small allen pinch bolt out and installed a Gr8 1/4 bolt. Its tightened to the point of breaking and the clamp is still loose. I am using a 1 1/8 lock collar to hold it all together temporarily. The thing is best thrown in the junk box for parts.

I bought the frame and the springer at different times when on sale. They were both(each) $99 with free shipping. Id be really bent if I paid more!

Frame is good. Its an earlier model with the closer spacing on the engine front mount. Easily slotted for later engines. I was amazed/pleased the tank didn't leak. Will slosh it anyway.

Thanks CCC!

I will probably "revisit" this fork on the pull down for paint. Its easy enough to take the play out of the rockers. What I don't like is the suspensions loading is handled by the upper brackets clamping force to the stem, which at present is non existent. I guess some shimming is in order.

Have been riding the build several miles each day and it has run flawlessly. There is none of the common vibes in the pedals, seat or bars at least at the speeds I have been running. Considering the heavy alternator rotor, steel starter cup and the auto clutch the rotational mass is considerable offering quite a heavy flywheel effect. Idle is so smooth too.
I like the wet clutch and the fact the primary reduction gears are in oil. My clutch engagement is quite low, just above slow idle. This allows plonking along at very slow speeds with the clutch fully engaged. I did a bit of trail riding and it was very good at it. The engine has good torque down low. Pulls strong form the get go until I back out at reasonable rpms for a new motor.

Am taking another look at the electric start option, though the "fixed" recoil is working well.

So an update.

Recoil finally terminated with the total failure of the starter pawl. Old style Snapper starter switch should be here today. Plan is to use a 5ah lipo for starting. Fits into a 2.5" tube. Heading for the Depot to find some PVC pipe and caps to make a battery "box". Switch is of the direct type eliminating the need for the solenoid and mucho wiring.

Sent pics and explanation of the recoil failure to our friends at Bikeberry. Hopefully will result in a warranty recoil. Will be good as a back up to the electric. As is DONT plan on using recoil only. Engine always starts first pull cold or hot its an easy starter. The recoil is just that bad!

Shame of it is this is an excellent engine. The electric start is a blessing and a curse of sorts. I find it overly complex for an MB.

If my bare bones starter system works then all is good!

We will see!

So the starter switch didn't make it and much to my dismay PVC pipe doesn't come in 2.5".
I'm no plumber obviously.

Reinstalled the electric start system and gave it a test. The 5ah 4s Lipo has no problem cranking the engine. This was at storage voltage of 3.8v/cell or 15.2v.
It cranks so easily that I doubt there is much load on the Lipo. Should give many starts between charges. Its a total loss system at this point.
Havent concluded if it possible to charge from the engines charge system. Its output is probably too low.
The battery will mount behind/below the seat in something I haven't found or made yet. Was looking for something to mimic a tool box. Right now its cable tied in place for testing. Compare it to the 7ah SLA.

Starting now on electrons.

The system was easy to set up. Realize this is basically a temporary set up while the engine is evaluated. Will be cleaned up later.
Works great! The starter is a geared unit instead of direct drive, really spins the engine on the 4s. It starts so quickly that the Lipo shouldn't be highly taxed load wise.

The starter switch is under the seat at present mounted to the post clamp. Its easy to use right handed while working the choke with the left.

So far I like it we will see how it goes. Actually have room under the seat to fit two 5ah packs in parallel for a 10ah starter pack. Got to get a boot for the battery at the start switch!

Sorry about the pics, the old camera hates indoor shots,

Thanks Curt!

Found I can easily reach the switch while sitting on the bike. Cool! I usually start while off the bike. Like it either way.

scratchbuilder said:

How about making a half of one of those behind the seatpost tool/oil box's. You see on boardwalker's? Half it right above the chain,pack all da stuff in it.

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Theres a seller on ebay selling a lower end boardie tool box like you are talking about. Wont fit according to his measurements. I also looked at used M/C tool boxes nothing looked promising.

Due to the rear rim brakes being flipped upside down to clear the V brake anchors points on the top there is precious little room behind the seat tube for such. Probably just use a 3" PVC tube behind the seat. Not going to get too extravagant on this build.

So spent a bunch of time tuning the basically untunable NT carb.

I mean you can change jets, needles, move the needles up and down etc and get a decent running engine in the mid to upper ranges but the lower 1/4-1/2 sucks. Having a bunch of these things I got violent with one with the smaller 14.3mm slide. Smaller bore is better on low end. I'm not a speed racer at least not with this build. Its about smooth tractability. This engine will pull cleanly from start to top end(under loading) which is nice. However it is overly rich below half when cruising along with the engine unloaded. Typical NT.

I wound up grinding about 3/16 of an inch off the back side of the slide and using thin washers to get half the drop of moving the circlip on the needle. I also filed a small window in the front of the slide to lean the idle a bit.

All this has worked out pretty well to eliminate low speed 4stroking. Not totally but say 90+% This was a challenge with the NT and not the engine so much. It has always run well otherwise.

I have to say I'm spoiled by the electric start. I must have used it a couple of hundred times over the hours fooling with the carb. The lipo still does not need charging.

Last bit is, fooling with the carb I let neglected to tighten the chain after it wore in and got caught a few miles from home with too loose a chain. Really was glad to have pedals this time! Set about making a tensioner. My only choice is spring loaded. As usual got to looking around at something to repurpose. Made a tensioner out of a brake caliper Used the stock idler bracket mounted under the engine and just modded the caliper to work. Works great! This is a rough out. Ignore the junk hardware.