Things went downhill abruptly...

Discussion in 'Motorized Bicycle Trouble Shooting' started by soulnull, Jun 13, 2019.

  1. soulnull

    soulnull New Member

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    I went the solder method because I wanted more flexibility for if I do decide to go with a different carburetor, which at this point I'm happy to say is notably further down the list :) and thank you. Still a novice, but try to do right by my motors, even if I don't know what right is all of the time yet.

    Pretty much my thoughts as well on rock, obviously prefer slightly rich over lean. On the oil aspect, I did upgrade to the "full synthetic" Walmart 2-stroke oil, but haven't gone all-in on any specific oil yet. Have read quite a bit, but it's been a lower priority the last few weeks a after the cylinder flaked out (figuratively and literally).
    I have no doubt I'm going to mess up this motor at some point.. I tend to learn the most by breaking things (in my defense, I'm usually breaking things by trying to fix or adjust them, and usually hit some kind of snag I cannot overcome).. I'm calling this my learning engine.. not intending to break it, but aware that I probably will at some point. I'm hoping by the time that happens, I'll know a lot more and will have made a decision on the kind of oil I want to commit to for when i actually pick a good engine, carburetor, etc.

    Thank you for the reply, happy to see my thought process isn't too crazy or out there thus far.
     
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  2. soulnull

    soulnull New Member

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    Well, for the sake of adding to the info here, I have updates. Luckily they're seemingly resolved (for now), so this is just to document it, in case someone in the future winds up googling similar issues and finds this place (kinda like how I stumbled onto this place)

    She's been running alright, but the top of the throttle was gone.. Like, I could rev almost to top and it was alright, but if I went past a certain point, it decelerated and bogged.. So clearly not right.

    Also, I'd be about 5 minutes into a ride and could feel heat coming off the engine.... And today I noticed the spark plug nut and acorn nuts are actually starting to discolor from the heat, and the engine was sizzling after I shut it down. Yeah, it still had rain on it, but sizzling? Yeah, no, that's not right.... Also, if it revved high under load, it clattered. Not a normal clatter, like metallic clapping. Obviously not a sound you'd want to hear at high speed.

    Despite thinking that getting it to stall out when choked showed it wasn't running too lean, it was still running way too lean.

    So I pulled the jet and used the bit I already used, but kinda making a point to scrape the sides to take some more off. That helped a notable amount.. Then I pulled the jet again and went up a size. Apparently when I rejetted it the very first time with that bit, the solder didn't stick and when I used that bit the first time, it just popped it through the hole, but not this time.

    So it's revving smoothly now, all through the band. Not as high as before, but two things affect that.. One, clearly it was running lean, so that high rev was probably not a good thing at all. And second, I am probably running closer to a 12:1 oil/gas ratio.. So this tank is quite oily. While trying to diagnose it, I added more oil to try to protect it as much as possible. Not sure if this is actually what I'm supposed to do, but seemed logical to do, especially since I had to get it to higher speeds to really diagnose the clattering and the 'no response' over 3/4 throttle issue, and really didn't feel great about doing so without at least trying to do something to try to protect it.

    And worth noting, all of the aforementioned problems have been resolved by further jet tweaking. I know I said 'good enough' in the previous post, but I'm not gonna let the thing run *that* lean.. If it's discoloring nuts and causing microcracks to appear in the spark plug boot, and making the carburetor almost too hot to touch, then that needed addressed immediately... Not ready to buy another engine yet, this one is still breaking in... Though I've probably reduced its life quite a bit with this recent lean issue :(
     
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  3. Greg58

    Greg58 Well-Known Member

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    Reading a spark plug takes some practice, its kinda old school and not used in today’s vehicles. But in my era the only cars on the road that had fuel injection were corvettes. I learned a lot about making power with the right air/ fuel ratio, leaner is faster, works in drag racing but not for long, the price of winning was replacing a lot of parts.
     
  4. soulnull

    soulnull New Member

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    Currently I'm wary of pulling the plug because it seems to want to be way too tight to not leak... but if the outside of the plug and the acorn nuts are turning rainbow-ish colors from the heat, then I can only imagine the inside isnt gonna look much better :(
     
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  5. indian22

    indian22 Well-Known Member

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    Some great stuff guys & covering well several oft recurring problems with the "kit" 2 strokes, carbs, mix ratios, synthetic oils, top end problems, heating issues etc. I love this stuff!

    Some of my general observations on building these critters to run decently & last for many hours of multi use riding. Not racing that's a whole different topic, but the basics are similar. First you got a bad top end & cylinder plating was bad. New jug $25. Ashfree semi synthetic or full synthetic...I use Lucas for 2 strokes. I've not had good fortune with the NT or Speed carbs, but some do. I use the RT, Sha clone Dellorto on some but quality is all over the place with these & the 18mm or 19mm real deal seems bullet proof. Same with the small Mikuni carb. The real thing is worth the price.

    Running hot. Allen suggested lubing the internals prior to assembly and after assembly turning the motor over (in the correct running direction) I use a variable speed drill to assist in this, for a few minutes at very slow speed and lightly lubing the bore during this process with the head off. I always replace the kit head with a well finned billet head more for cooling than performance with a midsize combustion chamber so as not to greatly alter compression ratio, just a bit of a bump and start with a thicker copper head gasket for break in. Jug base gasket stock gasket. Both these gaskets can be easily replaced to alter compression and timing later if you start to chase more power. Remember more power equals more heat and heat kills these motors.

    More friction equals more heat as well and though these are air cooled design the fuel mix not only serves to feed and lubricate the motor it also cools the motor internally. Since there is no oil reserve in the crank case/pan as is the case with 4 strokes, fuel flow needs to be continuous or the motor will build up too much heat, idling is bad and so is trying to compression brake (like a 4 stroke) to slow down. Use the brakes not the engine to brake. With clutch in keep blipping the throttle to keep the cool fuel mix flowing.

    All basic but some don't do it and thus the China kits get an even worse reputation. If you ride WOT much even the best of these motors won't last long and by that I mean hundreds of hours of riding. I have one bike that never had the head off until after 700 + hours of riding and even then it wasn't running poorly, I just wanted to convert it to a reed valve setup with third port and window piston.

    High rpm is a relative term, some kit engines struggle to get to 8,000 while slightly modified piston port engines with a pipe reach 12,000 plus. Engines can't handle that high number for long! What I look for as a builder is a motor that easily blasts past 8,000 & is climbing rapidly upward at that point. These are engines using slightly rich sittings, not much. just everyday riders that will last for a long time.

    Rick C.
     
    #25 indian22, Jun 30, 2019
    Last edited: Jun 30, 2019
  6. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    Your jet is too small!!

    When I solder my jets, I make it as big as possible (with very little 'sputtery feel')

    Another good way to feel it is when the engine feels a little sputtery but the sputter goes away as soon as you start going up a hill... That's when you know you're one size too big on the jet.
     
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  7. soulnull

    soulnull New Member

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    Jet was definitely too small for me, but I also have the needle at the 'halfway' setting.. Wouldn't have messed with the jet size if the thing wasn't running ridiculously rich even with the needle at the leanest setting. Less than 10 hours and the piston had blow-by, bogged at anything over about 12mph, and had absolutely no power.. Can't let it suffer under those conditions... And that's no fun to ride, either.

    Took it for a few rides today. Have a nice little consistent hill incline on the end of my road. Clutched down, did my u-turn, then started to climb. Thing held solid at 20mph, no problem, no bogging... And my favorite part? I can now touch the engine after a good 10 mile drive, even with the hill thrown in there! Yeah, it's still too warm to hold my hand to it, but whereas I could feel the heat blasting off of it before, now it's actually fairly cool for an engine containing thousands of explosions per minute.

    I do have the needle set at the middle position, and yeah, it's running slightly rich up to 3/4 (some pops, slightly burbly sound, etc).. Not very rich, but rich.. But the last 1/4 of the throttle is just absolute butter now. I'm fine letting it run rich on the bottom 3/4 since it's still breaking in. It still has plenty of power and isn't bogging down there, but sound-wise indicates rich.

    I've read that the needle seems to have the most effect on the bottom 3/4 and the top is almost all jet (please correct me if this is incorrect!)... If this is the case, then she's pretty much back to her former glory, and once I have more hours on it I can up the needle a notch to lean it out a bit.. But I want at least another 2 tanks of gas run through before I do that, and have a good idea of how much the oil/fuel ratio is going to truly affect the lean/rich equation.

    I've given it quite a few drives since fixing it, and today couldn't resist giving it a proper WOT test. About 30 seconds on a pretty much flat straight. Previous cylinder/carb tuning with 16:1 ratio got me 33mph. Now after finally getting it back into shape, albeit at probably a 12:1 ratio (gas in the bowl is dark blue, not light blue.. Definitely a very oily tank in that puppy), she hit 31. Without any pedal assisting (and admittedly pedal assisting on the 33mph run).. So pretty much back to how I remember it.

    Also worth noting: even with the previous setup working fine most of the time, that hill at the end of my road needed some pedal assistance.. Not much, basically just pedaled along without much effort, but it really wanted the extra help.. Even when it was running too lean, it wanted nothing to do with that hill.. But I'm happy to say that after the third rejetting, It went up the hill effortlessly this time. Buttery smooth, no pops, coughs, rattles, nothing. As smooth as an idling lawn mower, and chugged right up that persistent but slight incline with no complaints.

    The incline is 100 feet elevation change over 2000 feet.. Not sure what the comes out to in degrees or whatnot.. There's another much steeper one (50 feet elevation over 200 feet distance.. That's a tough hill!) but it's gravel, and my baby isn't ready for that challenge yet.

    I couldn't be happier with it's current progress.

    I am confused and concerned at how the carburetor went from working just fine to being way too rich, which seemed to happen right when the cylinder plating failed.. Made it very tricky to fully diagnose. Then I definitely overcorrected to try to fix that problem, but as I've said quite a bit in this thread, this is a learning engine and I fully expect to break it over time.. Though my goal is to run it as long as I can and learn as much as I can from it... And of course, share my trials and tribulations here to help others who may find themselves stalled out down this road with no pedals.
     
    #27 soulnull, Jul 1, 2019
    Last edited: Jul 1, 2019
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  8. indian22

    indian22 Well-Known Member

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    Easy fix hope lots of lessons learned during the process.


    Rick C.
     
  9. javy mcdees

    javy mcdees Active Member

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    I am still riding my bike but not today it rained but the dellorto is still to rich for me 1/4 throttle, 45 pilot should drop it again 42 maybe and another needle a fat one to make it leaner all around I think a w11 needle, other wise it runs swell for what it is now. just would like it leaner down low rpm to 1/4 throttle needs improving.
     
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