|
Post by paemt1 on Aug 28, 2012 20:23:48 GMT -5
Hey all,
I just installed some "parts" and need some of your knowledge.
I have a Sym DD50 and had soft-seized my original engine. I put in several new parts which I know is not the smartest thing to do because when you do have a problem (like I have) then it makes it difficult to track down the problem. That being said, this is what I have replaced:
75cc BBK 44mm crank(my old crank needed to be replaced because when I soft-seized the 50cc, the conrod bearings were also damaged) New variator and 9gram weights Rejetted the stock carb #82
I had a #88 in the stock carb but you fine folks told me that it was too large for my stock engine even though I had removed the intake manifold restriction and installed an aftermarket exhaust.
After I had installed the BBK, I attempted to place an #85 but could just not adjusted correctly. So I installed the #82 and have been "tinkering" with the a/f and idle screws most of the day. I started with the a/f screw at 2 1/2 turns out. Had to continue to adjust the screw to the right until it was only about 1/2 turn out to get the thing to stay running and not "bog" at 1/4-1/2 throttle. I was working on my "break-in" ride when, at about 40 mph, I felt the BBK kick in. AWSOME ;D. I didn't want to damage the cylinder so I let off the throttle. The old girl stalled. I let the scooter "free wheel" until I could pull over, stop and restart. It started right back up and I rode it home, SLOWLY. I made some minor adjustments, didn't seem to change much of anything. I took it for a second ride and the same thing happened. I decided to ride it to work, SLOWLY, because I am very lucky and can "tinker" at work. I was 3/4 of the way there. I started going down a hill and the scooter sped up. I attempted to slow down and let off the throttle and began to break. The scooter shut down as soon as I let off the throttle. This time, it free wheeled for a short time then the transmission grabbed and locked up the rear wheel. It destroyed my belt, of course, then started to free wheel again. I was able to get it to work with a little help from my co-workers who weren't too far away.
Two questions:
1. I did check my plug(not a new one but the only plug I have currently) and it was light grey. I believe that is too lean but if I adjust the carb and richer, it just boggs and will eventually stall.
2. Why is the bike stalling at speed when I let off the throttle?
I need all your expertise, please!!!!!
|
|
|
Post by wile on Aug 28, 2012 23:35:09 GMT -5
It may just be Idleing to low and the slider comes down and shuts all the air and gas off. Wile
|
|
|
Post by paemt1 on Aug 29, 2012 3:23:47 GMT -5
thanks Wile. I'll have to get a tach. That is one thing that I don't have.
|
|
|
Post by wile on Aug 29, 2012 12:44:20 GMT -5
You can try it just get the IDLE UP high enough that the REAR wheel starts to spin then back it off to where it stops spinning. You want it just where the Rear wheel WANTS to start to turn maybe a HAIR less. Wile
|
|
|
Post by paemt1 on Sept 8, 2012 21:32:12 GMT -5
Wile,
Would running too much 2T oil cause these symptoms?
|
|
|
Post by skuttadawg on Sept 8, 2012 21:46:41 GMT -5
Try adjusting the needle in the top of the carb . What size carb do you have a 17.5mm or 19mm ? I was running a 75MJ on my 49cc with airbox . I put in a 90 MJ with a small Uni which was a vent cover not the big red airfilter and wow it had more takeoff and midrange ran great . Put on the correct Uni it had some bog and soft seized .
Its now a BBK with 70 exhaust and Uni . The 90 it ran ok but I will need a larger jet but 110 was too big . The idle jet in mine is a 40 .
|
|
|
Post by paemt1 on Sept 11, 2012 13:15:58 GMT -5
Skutdawg,
I have the stock carb which is 12mm or 14mm. Not really sure. I've seen on-line that my scoot comes with a 12mm but the free online Symyang manual says it's a 14mm. Either way, it's stock.
|
|
|
Post by gregw on Sept 14, 2012 20:48:34 GMT -5
9 gram weights are way too heavy. Even for a two stroke with no aftermarket pipe. It will run like it's rich if it is operating lower than in it's intended rpm range (dictated by the cylinder design/port window placement). Unfortunately, anyone who told you that an 88 main jet installed on a scoot at 75cc with aftermarket pipe is too large, is a fool. In fact, it may be too small. Fiddling with the A/F mixture screw will not help when trying to adjust your carb for WOT. Change your variator weights to 6 gram or less (maybe even 4 gram like I am running), upjet to a 90+ (or 100) main jet and see how it acts. Two strokes are all the same. Chain saw's, weed wackers, dirt bikes, and scooters. Run the rpms high, and use the main jet as the rev limiter until you understand how it runs best (cardboard brown burn on the plug). I mean, if you're too rich, your motor will only rev so high, if you're too lean, it will rev to 12k+, then blow, or sieze (that does not mean it won't sieze sooner). A wise man said "err on the side of richness" if you are trying to learn how to tinker with these things... It will save money and time. Good luck!
|
|
|
Post by paemt1 on Sept 16, 2012 10:00:59 GMT -5
Greg,
Thanks for your advice. BTW, Wile was never referring yo my scoot seizing. This thread is about tuning and stalling, which he was referring to. I will definitely get some lighter weights cuz it is a dog (and not in a good DAWG way) at low end. Thanks again.
|
|
|
Post by paemt1 on Sept 26, 2012 21:40:40 GMT -5
OK Guys,
I need some advice. I finally got a belt and installed it. Checked my compression and it was 32-35 PSI. I thought it was a faulty tester from Harbor Freight because the same tester read 30 when I checked the old cylinder. i thought that it may have just been "stuck" and wouldn't go any higher. Unfortunately, I DID NOT check the compression immediately after I installed the BBK so I don't have a starting point. Anyway, I exchanged the compression tester and I got 35PSI with the new one. I had to use the kick-start but no matter how many kicks, it did not go any higher.
My question is where do I go from here? I assume that I should replace the rings. Anything else I should check? Intake it TOTALLY stock and untouched (except MJ changes). Could there be an issue with the reeds? I don't know enough about exactly what reeds do or how long they last(scoot has 2,500miles on it), just thinking about ANY suspects. I split the crank case and put in a new crank but I have NO OIL Leaks so I assume that is ok.
|
|
|
Post by sdeeze on Sept 27, 2012 8:04:19 GMT -5
OK Guys, I need some advice. I finally got a belt and installed it. Checked my compression and it was 32-35 PSI. My question is where do I go from here? I assume that I should replace the rings. Anything else I should check? Intake it TOTALLY stock and untouched (except MJ changes). Could there be an issue with the reeds? I don't know enough about exactly what reeds do or how long they last(scoot has 2,500miles on it), just thinking about ANY suspects. I split the crank case and put in a new crank but I have NO OIL Leaks so I assume that is ok. I'm not sure what year your scooter is from but I've been running driving a 2006 SYM DD50 for about 4 years now and have put ~12,000 miles on it. I have not had to replace the reeds in all this time. Also, I'm about 98% sure that you're rocking a 12mm Keihin carb. I'm also rocking a similar setup, and have not upgraded my carb either. While getting a new one is next on my to-do list, I've found that once I upjetted to a #95 that I'm getting a nice color on my sparkplug. I do have to say, with compression that low, I think it almost has to be something with the cylinder itself. I would just double check on any intake or exhaust leaks which might be throwing the compression off as I think it's possible that something like that may be affecting your compression a little bit, but it just sounds like the core of the problem has something to do with the cylinder itself. One possible suggestion, and this is really irrespective of your current compression problem, would be to switch over from using an oil tank/pump setup to premixing your gas and oil. If you're going to be doing any more tuning for your new setup this will help you calibrate since you'll actually know how much oil is being added at any throttle level. I ended up having to switch over to premix when my original oil pump decided it just wanted to start dumping oil in at all times. Not to scare you or anything, but I wouldn't be surprised if the stock oil pump decides to go wonky on you at some point. I know that's kind of vague, so sorry for that, but let me know if there is anything else I can answer. I've included a picture of my carb, which I'm almost certain is a 12mm kehin so that you can compare with yours. Attachments:
|
|
|
Post by paemt1 on Sept 27, 2012 13:44:52 GMT -5
Thanks Sdeeze,
Yes I have a 2007 and didn't think that it was the reeds either but just at a loss as to what is happening with my compression. I have thought of going pre-mix as well. I know allot on the forum suggest that. I will double check all the suspects you mentioned. I really appreciate your input especially since you have the same scooter as myself. your comments are welcome anytime. And yes,my carb is the stock 12mm carb but just slightly different.
|
|
|
Post by sdeeze on Sept 27, 2012 15:35:39 GMT -5
Thanks Sdeeze, Yes I have a 2007 and didn't think that it was the reeds either but just at a loss as to what is happening with my compression. I have thought of going pre-mix as well. I know allot on the forum suggest that. I will double check all the suspects you mentioned. I really appreciate your input especially since you have the same scooter as myself. your comments are welcome anytime. And yes,my carb is the stock 12mm carb but just slightly different. Well, I'm honestly just glad I could help out a fellow DD50 owner as I don't believe that there are all that many of us out there, at least here in the US. I'm sure that you've been all over the forums looking up how to check the status of various cylinder/piston components. The link below is the best thread I could find about the situation here on the boards but it's certainty outside of what I know how to tinker with on a scooter. scootdawg.proboards.com/index.cgi?action=display&board=discussion&thread=48506&page=1I'm not sure what your financial situation is now is going to be in the future, or whether you have any reputable scooter dealers/shops in your neck of the woods, but it might be worth getting a professional to take a look. I only say that because, while I haven't done this myself, some of the things (like cylinder clearance) have a small optimum threshold that would likely require somewhat specialized tools to even measure. Also, they're more likely to have any gaskets or rings on hand for replacement whereas you might have to spend up to a week waiting for parts to be delivered through the mail (although, depending, they might too). If you do decide to get it checked out perhaps you could get them to plug your oil pump and remove the tank? In addition, since you appear to be knowledgeable about your problem, you could instruct the shop to only check out the cylinder and anything directly related to save some money, instead of giving them free reign to check out every single possible thing. Also, and I should have noticed the exact CC of your BBK earlier, but I think you may have to upgrade to a larger carb, something in the 17-19mm range. I only say this because I'm currently utilizing a 62cc BBK and new exhaust pipe and I'm pretty sure that I'm at the outer limit of what my carb can handle. Well I feel kind of like a Debbie Downer with all this advice I'm throwing your way. However, don't let it get you down because once you get that scooter tuned right, with the setup you have, you'll be able to accelerate like a bat out of hell and go up hills no problem. Also, from what I've read and first hand experience, the DD50 is a quality scooter that should last you for many years to come. Good luck! Here's to hoping you get all of this sorted out and comfortably back on the road as soon as possible.
|
|
|
Post by paemt1 on Sept 27, 2012 19:52:58 GMT -5
Thank you sdeeze. I really appreciate you assistance. i was just about to consult a local repair shop.
|
|
|
Post by sdeeze on Sept 27, 2012 21:55:05 GMT -5
Thank you sdeeze. I really appreciate you assistance. i was just about to consult a local repair shop. For a situation like this, I think this is probably the best choice. Whenever I think about doing work like this, I always tend to forget that even if I can follow the guides online (like all the awesome ones provided here at scootdawg), that often times when I get to the component to check that I really have no idea what exactly I'm looking for and can't interpret the results of whatever visual checks or measurements I make. It took me a while to even be able to read a spark plug well (and even now I kind of doubt myself sometimes). Also, if you don't truly know what you're doing because it's your first time (I'm assuming first but I could be wrong if you intalled the BBK yourself) you'll be flipping out in the back of your mind for the first couple hundred miles wondering if you solved the problem and put everything back in place correctly, and if you're on the edge of a huge problem. I'm not saying that doing a check and/or repair of this caliber is necessarily out of reach of someone who has done all their homework online, is really familiar with their scooter, and has all the proper tools but I wouldn't feel comfortable doing it if it was my only scooter and I didn't have the backup funds for professional help if things went terribly wrong. Also, it's the beginning of this marvelous fall riding season, I'm inclined to pay a little extra if that means I'm back out sooner during this spectacular weather. I'm not sure what kind of work/storage space you have available for the scoot, but perhaps this Winter might be a good to spend a little time getting more familiar with your engine block. I'm hoping to, but I don't want to screw anything up for this fall though. Also, please let me know what the cause of the low compression is/was whenever you find out. I'm kind of curious as to what it could be. Also, any pictures of broken/smashed/burned components that were involved can be a nice bonus if you can get them back. It might not be a bad idea to spend a few minutes chatting with whomever you can (of course mechanic doing work is best person but not always available) about what exactly was causing the problem and what possible indications you could have looked for on your own. Even better would be to see if they can take a picture of whatever the culprit was, in it's dysfunctional state, so you can see exactly what it looked like when having a problem (and share it with us). They might not do it, but no harm in asking. Also, if you can find a knowledgeable person, ask about your current setup and possibly get an opinion on how it's running (rich, lean, or perfect). You can probably do that on your own, but since you've added such an upgraded setup it'd be good to at least get a second opinion about it, even if you just conclude the person's wrong. I just kind of think that if you're using a #88 main jet that you're likely running lean but all I can do is speculate. Again, good luck, let us know how it works out.
|
|