stock spark + exhaust 50cc

tseekr379

tseekr379

New Member
Hey everyone. I am wanting to make some changes to note any difference in performance. Since I am not too mechanically inclined, and most of my knowledge is theoretical, I must rely on a mechanic who 1. Knows what he is doing and 2. Will not screw me over.

What could you tell me about modifying/replacing the exhaust, without afterwards making adequate adjustments to the carb, etc.? If I changed to the sparky to an NGK Iridium or any other, would I have to make any other changes besides gapping?

I don't want to modify/replace any parts without making the proper adjustments afterwards.

Plus, I don't know if I am getting an air leak, and how that is affecting performance as well. Seems it doesn't idle as strongly in the past 50km, no matter how much I adjust the idle screw. Then, after warming up and running for about 10 or 15 mintues, when I come to a full stop, clutch disengaged, motor dies.

It could be so many things, but I'm not downcast, as I've read somewhere "these little motors never break". There is hope!

Any advice on these problems would be greatly appreciated.
 
I just love how there are 74 views and no responses... doesn't put much confidence into the purpose of the forums... thanks and no thanks?
 
Any alteration to the intake/exhaust should be verified for proper air/fuel mix by examining the spark plug electrode for the proper coloration (black = too rich/gray = too lean, lookin' for a tan/coffee color) & Iridium plugs come pre-gapped (.030 is about optimum depending on ign system).

It's almost impossible to diagnose carb problems w/o knowing which carb you have, but generally speaking if you've an air/vacuum leak you'll be running lean (chk plug color) and often your idle will be irregular, but usually too high...

tseekr379 said:
I just love how there are 74 views and no responses... doesn't put much confidence into the purpose of the forums... thanks and no thanks?
Click to expand...

While ofc the point of the forum is to help & share with others... the questions you've asked are so basic as to have been answered thousands of times before, you may wish to check out this subforum for some introductory information: http://motorbicycling.com/forumdisplay.php?f=30 Classic Instructions for Building and Repairing Motorized Bicycle Engine Kits as well as http://motorbicycling.com/forumdisplay.php?f=51 Intake & Exhaust & http://motorbicycling.com/forumdisplay.php?f=50 Lighting and Electrical

While we don't penalize folks for not using the search as that's downright unfriendly, you may find it's of far more use than waiting for someone else to find the answers you seek... those who know may have moved on to other things & those who don't obv can't help lol

You may also get more prompt assistance with a more specific thread title, such as 'Help needed with (whatever)' *shrug*
 
Thanks man. Like you said, some questions are so basic, that sometimes, after searching and reading hundreds of threads, I can't find 'specifics'. I no longer have an air leak, and I will NOT be replacing any stock parts (except for maybe the clutch lever, which is quite crappy and gave out on me yesterday). Any parts I do replace will be acquired through ebay, from official vendors.

I also did a ton of researching to see why my motor has such difficulty starting ever since I changed the needle to the leanest setting. It's not so much difficulty, it just takes longer to warm up now. But I still couldn't find any relation from carb needle setting -----> longer motor warm up.

You see, sometimes, you just HAVE to ask questions, otherwise, you learn the very hard way, or you don't learn at all. Thanks again... I will continue my search for why it's taking so damn long to start up when it was much easier before the carb needle setting. Btw, my carb is a NTTC carb. From what I gathered on the forums using the search feature, I may need to upgrade spark for faster warm up?
 
When you fixed the air leak, you ran richer, ya then corrected it by changing the clip to it's leanest setting - but did you check plug color after running it? It gets tricky for me to advise specific carb/jet settings as you're at "9,000 ft." and I'm at sea level... sometimes under, but that's another story lol

Ya may need to rejet for optimum performance, but you'd hafta ask someone w/a similar altitude *shrug*

Are you still running the stock plug? That one is really poor quality, many prefer the NGK B6HS gapped to .030 - tho I'd confirm fuel/air mix before messing w/heat ranges ofc.

TBH... I've noticed small two strokes tend to be... picky sometimes - not that they run poorly or are hard to start, but that each one has it's own "tricks" or method that works best. Some like a tap on the primer, some like the choke, some both & some nothin' but the throttle *shrug* They're defo weather & temperature sensitive too. Not a big deal, but something to consider ;)

Does it run well once warmed up?
 
Yes, the spark plug color is fine, a nice tan coffee color. The motor runs beautifully when warmed up, it is just harder to start now that that needle is leaner. I am going to run out right now and inquire about the NGK B6HS, since mine is not heavily modified or anything.

The problem with this is not so much my altitude, but the varying weather here in Quito! It will be cold in the morning, then hot during the day and maybe cold again in the afternoon. So when considering spark plugs, I can't resort to a "hot" or "cold" spark replacement, because I have both temperatures, more than once a day, at varying intervals. I need something obviously better than stock, but that is more "neutral" so to say.

Would I need to properly gap if I replaced the stock spark to a B6HS? I'm wondering if I could tackle this myself, or perhaps I could get someone to help me. You have to be careful of who you let handle your MB over here. Getting the wrong people involved is much more trouble than it is worth!

Like I said, once warmed up, the motor runs great, especially now that it is leaner and there is more air in the mix.
 
im in denver co...almost as high of elevation...but alot closer.....we have to run lean...def check your plug...for 20 us you can get a infrared temp reader....you can use that to check your operating temps at the plug....it can be a basic idea of how the motor is running...keep in mind that at really high altitude the little 2 strokes dont breath extremely well ...so its gonna be doggy till you put a plug /exhaust and port some things.....with that said....with out buying a bunch of stuff.. the plug will help as well as getting your mix ratios right for your altitude...i personally run 32:1 on 2 stroke mineral oil and that seems to work pretty good at this elevation...might help you as well.....and you dont NEED the iridium plug but its nice im running a bpr7hs at this alititude and it works great

.30 for gap...and a resistor type plug will not interfere with a electronic speedometer...but gives a tiny bit less power from what i hear
 
Sweet, good ta hear tseekr (^)

Yea, while many new plugs are pretty close it's best to at least check the gap to be sure, .030 is a good starting point, some like narrower & some a lil wider, but the wider the gap the more power is needed to jump the gap and these kits don't have much to spare lol

The exception would be the Iridium plugs, they're defo pre-gapped and you may break the electrode if you try and alter it *shrug* I run one and I like it, but TBH it's more about plug longevity and anti-fouling than any perceivable performance gain...

You can defo "tackle it" yourself, pick up a gapping tool at any automotive parts store, sometimes they're even giving them away free as keychains - it's a simple adjustment & part of a basic tuneup.

Honestly? If yer happy w/how it runs and you've got the perfect plug coloration I'd not mess w/it beyond trying a quality, gapped plug... give that a whirl and see :)
 
Thanks! I was reading another post on the forums, and Venice Motor Bikes suggested:

"That spark plug is too cold! (referring to a B7) A colder plug won't make your engine run cooler, it'll just foul & not burn off the gas & oil from itself. Use a NGK B5HS.

High altitude means less air, so you also need to have less fuel going into the mix.
That 'splatty' sound that it's making is from being too rich. Change the plug & raise the c clip on the carb needle to the top notch (farthest from the point) & tell us how it's doing."


I have raised the c clip up to the top notch, and it has improved greatly. I am running 32:1 on this third gallon, after running the first two gallons at 24:1 (which I think was too much oil, personally). Rejetting isn't an option right now, as there are no main jets here, and people don't seem to have wire drill bits that small over here. I tried inserting a very fine copper wire strand and that created problems with the throttle response, so I took it out and it runs great with just the needle adjusted. But the spark plug is an issue, I am not sure on which one. Some have said the B6, others B7, and now I see that B5 may be my best option?

You're right about these little motors not breathing right to begin at high altitudes, but will somebody guide me in the right direction for the spark plug and which one to get? Infrared temp reader is not an option here, they are probably 10x as costly as well (import taxes).

I will do porting and all the other fun stuff in time, perhaps after break in. Right now, basics are my priorities. Also, until I can find a trustworthy mechanic that won't screw anything up (my motor or my wallet).

I am VERY happy with the performance, I just want it to start up faster! I don't want to damage anything installing an Iridium, but if it won't hurt to try, why not?
 
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the guys at venice know what they are doing...but they are really really low in altitude....i grew up near them...thin atmosphere and a really hot plug...the 5...may create problems...thats why i suggested the 7...for the record...i ran the hotter plugs when i was in california because it was needed for the heav air at lower altitude...just a suggestion...if your getting the right burn now just upgrade the plug and stay in the same heat range...probably a 4?...thats what mine was stock .....the temp differences that we get here are prbably close to the extremes you get...good example...it was 40F when i woke up...its now close to 55F..2hrs later...it will be around 60 till abut 6 then it will drop sharply again...the joys of high altitude...being higher up its probably more extreme for you in changes....but my point is...humidity affects us more then ambient temperature up this high....food for thought...wish you the best of luck...your going in the right direction!
 
Wait... I was just reading about the spark plug gap and how it could affect how your motor starts, and performance... I think when I increased the spark plug gap by a bit, my motor got harder to start. Not because of my needle being leanest, which I thought before. Ok, I am going to see if I can get that gap measured and see if regulating it changes anything.
 
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GOOD FOR YOU! ask-think-try ----you're going to get it worked out. I'm at 1,900 feet and I'm still working stuff out-if my motor "4strokes" I lean the gas-if running the choke helps I enrich the gas- I run as wet with the oil as I can with out failing the plug 32\1 is good for me-vac leaks can be found by spraying WD40 on the suspected part with the motor running if the idle changes or the exhaust gets smoky you have a leak.
 
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