Puzzle on my Jackpiner

[lksseven]

1972 Piner:  

Got this bike end of August.  Rode it several times, to see how it acted, and what it needed.  Last time I rode it 6 weeks ago, it was flowing gas out of the overflow tube almost the whole time while I was riding.  I replaced the bowl, the throttle cable (different reason), jet needle, needle jet, atomizer.  Couldn't replace the slide (Bing didn't have one) - and the existing slide has an idle screw worn notch, but I can't tell if it's big enough to be a problem.  I started it up after many kicks, took off on a warm up ride, got to the bottom of my infamous "6-day Hill" from this summer, 3 blocks from the house, turned around and, you guessed it, it bogged on the uphill grade (mild) and died.  What's different from the 125 6-day this summer - it's 40 degrees cooler (65 instead of 105), and the bike would start again, but not go under load.

So I figured, must be the Motoplat going bad on this one, too (as that turned out to be the problem with the 125), and I decided not to push it for 3 months before getting around to the ignition.

Today I installed an MZB ignition, got a big fat blue spark, kicked it started (after 8 or 9 kicks), took off on a check ride, and, yep, it died at the bottom of the hill (this hill-bottom could be the Penton Bermuda Triangle).   Long story wrapup -
- it will start,
- it will run,
- I cannot get it to idle stably by itself yet
- within a couple of minutes it will begin to bog.  
- If I activate the choke about 1/2", it will run better for a little bit, then bog.  
- If I gas it past half throttle, it doesn't climb on the pipe, just kind of maintains its casual revs.

I've got good grounds.  

Any ideas, other than replace the entire carb?

Larry Seale
I choose to ride

[cubfan1968]

Hi Larry, maybe your cursed. Did you clean the carb? Also did you try blowing out the idle jet and leveling out the float? Wish you luck.

Rod Whitman
1972 6 Day (Rider)
1972 6 Day (Project)

[behindbars]

Hi Larry. Sounds like your bike is running very lean. I'd check the float level, but also check for an air leak. How is the bike jetted compared to the stock settings? Have you pulled the flywheel cover off and checked the play in the main bearing? A loose bearing can cause an air leak at the main seal that you just can't see, especially with a old hardened seal that no longer has any flex left in it. Also, a 40 degree swing in temperature will wreak havok on jetting. If it ran good at 100 degrees it will be lean at 65. Your bike probably makes it down the hill fine as it is under a very light load. Once you try to go back up the lean jetting will not develope enough power to pull you back up as now it has an incline to deal with. [xx(]

[lksseven]

I'll enrich the needle one notch and see what happens. (it was another bike - 125 - that gave me fits last summer, although all's well that ends well, the 125 ran superbly at the RR in Arkansas) - thanks!

Rod,  I'm confident that I thoroughly cleaned the carb, and set the float level correctly, but I'll definitely check both those things again when I 'rich' the needle one notch.

I have no experience with bearings, so I wouldn't know what I was looking at.  Maybe I can schmooze Dave McCullough to help me look at that, if it comes to it.

Larry Seale
I choose to ride

[rob w]

Larry.......Deja vu ?

[rob w]

Larry.....Deja vu ?










Did you ever get the gas to stop running out of the floatbowl's overflow tube?

[john durrill]

Larry,
 The lack of a stable idle is a key symptom. Raiseing the needle wont help the idle. It does sound like a lean condition. Could you post what you have for jets installed and the size of the Bing thats on it?
 The vaporizer does have the cutaway facing the engine right? Watch how the needle clip is locked in place also. Look at the book and make sure the parts are in the right order.
 Did the bike clean out and run up in RPM when you first got it?
It should idle like a clock if the mix is right when the slide is at rest and idle screw adjusted right.
 John D.

[lksseven]

John,
I'll post jet sizes and the Bing size (think it's a 32mm, type 54) in the next day or two, once I pull it.

I'll check the vaporizer orientation.

When I got the bike, it was a little reluctant to start and keep running (it would catch, die, catch, die, catch, die, then finally catch and stay running), and , and it didn't initially run all that clean and ramp up tightly.  It seemed to do better after I tinkered with it some, then the temperature cooled off and the bike started flowing gas almost non-stop that last time out.   Rob, It doesn't flow gas out the overflow tube indiscriminately anymore, though.

If the slide has deteriorated due to the notch being work by the idle screw, would that be a factor here?

Larry Seale
I choose to ride

[behindbars]

Hi Larry. It's very easy to check the flywheel side main bearing. Just remove the cover and give the flywheel a tug up and down. There should be ZERO play. Now granted a bike can still run well with a slightly worn bearing, but add a hardened seal into the mix and now you can easily suck air as a hardened seal will not flex with the wobbly bearing...it will just distort and allow air into the crankcase and cause a lean condition. This is a very common problem with old 2 strokes. It's also important to remember that jetting is very sensitive to changes in temperature and humidity. If your last run was at 100 degrees and the bike ran well, it should be dangerously lean at 65 if it was jetted cleanly for 100 degrees. If it was jetted right last summer, merely changing the clip position will not be enough of a correction for the colder denser air and it will still be lean on top. If your jetting is stock, I'd say you have a leak somewhere as normally stock jetting tends to be a little rich for safety's sake.
Hope this helps
James

[john durrill]

Larry,
 We cant tell from here how bad the wear is where the idle screw touches the slide. I would say as long as the slide moves up and down when you adjust the screw it should work. make sure that the throttle cable and the choke cables are adjusted correctly, enough free play.
 Check the main bearings for play like James said. Dont be fooled by play from side to side when you do this. The 175 should have some play from side to side to run right. not more than .010 of an inch i would think though.
 Usually when the mag side seal is leaking you see a wet area just below , running up to the seal it self. That seal is mounted in a removable plate on the KTM engines and can be replaced with out much trouble.
 I would clean out the pipe and end cap by burning it out and run a compression test on the engine at the same time. If the base gasket or head gasket are leaking that will show up as a wet area also over time.
Best we can do for now with what we know.
John D.

[Doug Wilford]

Larry;   Flowing gas out of the overflow!  I would say you need a new float needle and seat.   Bing has them as a kit.   It is very difficult to determine to lean or to rich but there should never be overflowing fuel all the time.    Have fun, Doug

[wolfmanonapenton]

Its suck'in gear oil or you have a vacum leak,Sound like a primary main seal,could be timing,or something making a ground![B)]

[wolfmanonapenton]

Read your Plugs?most important?[:0]

[lksseven]

Doug,
I put a new float needle in it - didn't change out the float needle seat, but it isn't over overflowing gas, now, though..

It hasn't run long enough for me to get a read on the spark plug.

Rob W, it's deja vu all over again

Type 84, 32mm, stock needle (I think I put it on first notch - it had been on 2nd notch - I'll move it back).

John,  I have an idea - what you said about making sure parts on in the right order .... I'll let you know

Here's a minor rant - installed an MZB Saturday, and the kit didn't include a length of spark plug blank wire to connect the cap to the coil.  For that kind of money, not to include 30 cents of wire makes my central nervous system produce sparks of its own (cost me an hour and a half to stop, clean up, drive to cycle shop and get the wire, then return, all in Saturday traffic, which is always a  martini-inducing adventure) .  Airlines, travel agencies, insurance companies, manufacturers across the board - I've just about had it with the trend to nickel and dime customers at every opportunity .... Aaaargh!

Larry Seale
I choose to ride

[rd400pi]

Larry,
  Did you check with your MZB supplier on the coil to plug cap lead?  Mine came with all required pieces so, it almost seems like it got misplaced.  Hard to imagine it would actually come without that piece.  Good luck and I'll talk with you this weekend.

  Mike Husted