Re: Almost no compression on 78 maxi

roots to wings /

Id need video with sound on at this point.

Re: Almost no compression on 78 maxi

https://youtube.com/shorts/MfjzyVTyXq8?feature=share

Here you go!

I was holding the clutch (and throttle) open for all kicks

Re: Almost no compression on 78 maxi

as you can see the flywheel either doesn't spin or turns an inch or two

Re: Almost no compression on 78 maxi

So pulling the clutch lever actuates the arm on the clutch cover, which turns a semicircular rod beneath it, which presses the starter plate against the starter side of the clutch. When you pedal the bike while this is happening, that pressure forces the clutch to turn, which turns the crank, which also turns the flywheel.

If the pressure against the starter plate isn’t strong enough, however, it just slips, and this is not at all uncommon. The solution in most cases is just to tighten the clutch cable, either with the nuts on the adjuster at one end or by pulling the cable a little further through the hole on the lever. If you look at it, you’ll see what I mean. Give that a shot and see what happens.

Re: Almost no compression on 78 maxi

Thanks Chinatown! I think my adjuster is maxed out so I'll try pulling the cable, will report tomorrow :) You guys have been incredibly patient

Re: Almost no compression on 78 maxi

Adjusted the clutch cable, its finally trying!

Gonna keep trying to start for a bit then put the old carb on if I have no luck

https://youtube.com/shorts/B6LUyfg53Bg?feature=share

Re: Almost no compression on 78 maxi

Nice! Try kicking it over without opening the throttle. Sometimes they’re temperamental at start, and too much gas can throw them off.

Re: Almost no compression on 78 maxi

I put the old carb on (temporarily, wanna replace it with the new one as soon as I can get it running since oldie is leaking a lot) and tried kicking without opening the throttle, no luck. When it was running last year it had a high flow air filter on, maybe I'll try with it on but idk if it makes much difference. Legs are pretty sore though so I'll have to take a break haha

Maybe I'll look into my spark a little deeper now? Idk

Re: Almost no compression on 78 maxi

^might be worth mentioning that one time while kicking with the new carb a little bit of smoke came out of the carb's air intake

Now I think fuel isn't getting to the engine. I turned the flywheel by hand a few times with the spark plug in, removed spark plug and stuck a paper towel in the hole. Didn't get wet but there was some black residue.

After googling it seems like if you're not getting fuel in the engine, people point to the carb and fuel line. I have a new fuel line, filter and tried with a new carb and don't think I was getting fuel even then. Any other reasons why fuel wouldn't be getting to the engine?

Re: Almost no compression on 78 maxi

Have you checked for spark recently? I reread the whole thread and I don't see it mentioned anywhere.

Re: Almost no compression on 78 maxi

> Mike Boyd Wrote:

> -------------------------------------------------------

> Have you checked for spark recently? I reread the whole thread and I

> don't see it mentioned anywhere.

Checked a couple weeks ago, I got a new plug but only tested it a couple times. The spark could have been bigger but it was light out so I just assumed it was probably fine, bigger than it looked but I was convinced compression was my issue at the time anyways. I'll probably look into that too, clean my points or whatever

Re: Almost no compression on 78 maxi

If you turn off the petcock, take the carb off the intake, unscrew the bowl, and then turn the petcock back on, you can see if fuel is flowing through appropriately. If it is, use this opportunity to check the jet for any debris that might be blocking it. If you pass both tests, the movement of the piston should create a vacuum that pulls your fuel/air mixture through the intake and into the cylinder, so give it a shot but kick it over rather than doing it by hand (I’m spacing right now on whether it might Wes more force than just turning it).

Forgive me if you’ve answered this already but has the timing been confirmed at somewhere around 16 degrees before top dead center? If it’s off too much, even fuel, spark, and compression won’t get it started.

Re: Almost no compression on 78 maxi

I'll test the carbs flow tomorrow

No, I haven't checked the timing. Not sure how but I'm sure I can just watch somethin on youtube that explains it, I'll give that a shot tomorrow as well

Re: Almost no compression on 78 maxi

Fuel flows through the jet - I plan on setting the timing tomorrow

Re: Almost no compression on 78 maxi

So I sat down to check for spark and all of the sudden I have none... I did earlier a few weeks ago. Checked the timing and it's at something crazy like 50 degrees BTDC. Can timing that bad cause no spark? Not sure how I got here, I haven't messed with any of the electricals besides connecting all the wires to the rubber terminal after I put the engine back on. I check for spark a little after I wired everything again and I had it. What could've happened?

Re: Almost no compression on 78 maxi

Ugh. I thought I was loosening the screws for the stator but it was the magnets. Spent like 10 minutes trying to get one loose too. I saw the coil move a bit and now both top magnets are scraping against the flywheel.

20210607_170415.jpg

Re: Almost no compression on 78 maxi

Bad timing will reduce performance or even keep your bike from starting, but it won’t eliminate spark. If the spark trouble began after you put the engine back on, then it’s probably just some wire connection and easy to fix once you identify it. Prob want to concentrate on the ignition circuit, which is usually a blue wire (goes to the HT coil, which also has its own ground) and a blue wire with black stripe (goes to ground but also powers the horn if you have one, so for troubleshooting just ground it).

Re: Almost no compression on 78 maxi

> Aidan Schmidt Wrote:

> -------------------------------------------------------

> now both top magnets are scraping against the

> flywheel.

Don’t worry. The magnets on the flywheel just pulled the coils into contact with them. Fixing it is easy.

Remove the flywheel. DON’T LOSE THE WOODRUFF KEY. Loosen (but don’t remove) all four of those coil bolts. With your fingers, push the coils toward the center of the stator plate. You are pushing them away from where the magnets would sit, toward the crank. Tighten the bolts again, keeping the coils in that spot. Then replace the flywheel, being sure to align the slot with the woodruff key THAT YOU DIDN’T LOSE, and torque it down again.

Get a business card and cut it in half the long way. Through the slots in the flywheel, slip those slices between the armatures of the top set of coils and the magnets in the flywheel. Then loosen the coil bolts again. The magnets will pull the coils outward, but the business card pieces will keep them from making contact. Now tighten the bolts and remove the cards.

Repeat for the lower coils. You have just set what’s known as air gap. (edited)

Re: Almost no compression on 78 maxi

> Aidan Schmidt Wrote:

> -------------------------------------------------------

>

> I'm also not 100% confident that I rewired it correctly (when I took the

> throttle off I accidentally disconnected the two wires coming out of it,

> may have switched them up when I reconnected them), could that be the

> issue?

Disconnect your kill at the wiring block. Make sure your ignition wiring is correct as written above.

The zen of mopeds is that you can just go through the same checklists to identify problems each time. Let's say you had spark at one time but then lost it. Instead of trying to backtrack in your brain what the culprit might be and fixating on that, just start from scratch and go through all the steps you would normally do to check for spark as though you had never touched it before. Use Wiki and Fred's Guide to help.

Good luck!

Re: Almost no compression on 78 maxi

Thanks! I messed with it a bit before seeing that response, I just loosened the screws again, pried the coils with a flathead towards the center so the magnets weren't touching and tightened them again. No more grinding, but if you think I should go back and do it the way you described I'll do that.

You were right about the wiring. I checked the terminal and one wire had come loose. It's back in place now. I wish I had checked that before messing with the stator.

So now I have to get the stator in a good place, but I'm very lost. The two marks I made for the top of the piston's motion are like a mm apart, so my TDC is pretty much directly on the other side of the flywheel. But my ignition points open a little before the top of the motion, not before TDC. As in the point where it opens is almost on the opposite end of the flywheel from my TDC mark. Rotating the stator doesn't seem to make a big enough difference to correct it.

Re: Almost no compression on 78 maxi

YYYYEEEEEEAAAAAAAAHHHHG

Re: Almost no compression on 78 maxi

Nice! Proof of concept!

Now fix your points gap and your timing :)

Re: Almost no compression on 78 maxi

> Mike Boyd Wrote:

> -------------------------------------------------------

> Nice! Proof of concept!

>

> Now fix your points gap and your timing :)

Will do!

As I said above, it seems like my timing is WILDLY off and I'm not sure what to do about that (point opens much closer to top than tdc, cant rotate the stator enough to make a difference

Re: Almost no compression on 78 maxi

Also thank you so much to everybody who's replied here, I obviously couldn't have done it without you! Almost gave up a couple times and took it to a repair guy so I'm very glad I stuck with it :)

Re: Almost no compression on 78 maxi

Going to make a new thread for how to fix my points opening opposite of tdc - this one has gone on long enough I think haha

Re: Almost no compression on 78 maxi

I love it when the repair threads end with an actual repair. It seems like a lot of these end with no resolution, and we have no idea if the person lived happily ever after or just gave up and sold the bike.

Re: Almost no compression on 78 maxi

> Chinatown Kicks Wrote:

> -------------------------------------------------------

> I love it when the repair threads end with an actual repair. It seems

> like a lot of these end with no resolution, and we have no idea if the

> person lived happily ever after or just gave up and sold the bike.

Thank you especially for your help, you contributed quite a bit!

Here's the new thread if you're interested, because spoiler alert it no longer starts haha so I guess the fight continues. I promise I'll continue to update :)

https://www.mopedarmy.com/forums/read.php?6,4470031,4470047,flat=1#msg-4470047

Re: Almost no compression on 78 maxi

Wow good work on getting it to start!!

Seriously. Many folks would have given up and left this thread to die.

Welcome to mopeds. Someday you will revisit this thread and laugh.

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