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Post by endru on Aug 28, 2013 6:20:51 GMT -5
[replyingto=skuttadawg]skuttadawg[/replyingto]I only did the head replacement, the big bore piston and cylinder had been installed for a few months now and running well. When I pulled off the old head I didn't take the whole top end off, but inspected the cylinder wall and piston head and they looked good to the naked eye. Valve clearance I set at the typical .10mm intake and .12mm exhaust (that's .004 and .005 inches). In the end I did not upjet. With my stock 19mm carb I always seemed to get rich mixtures with the jet sizes people typically use for a bbk. So before the new head I was obliged to run with a mere 80. I had no backfiring and the plug looked good enough... not coffee colored but not white. So with the new head I jumped right up to an  , and the scooter ran like crap, stuttering at anything more than 1/4 throttle. So I went up to a 92 and it was much worse, then back down to the 80 since I don't have an  . I just now went out to do the plug chop and it's definitely lean. So the question is, is the smoke coming because I completely ruined the top end, or will that go away if I upjet to an ? I guess I'll have to just try it and find out. Would a compression test be a good diagnosis of the condition of the piston and rings? I'm just appalled that this kind of damage could happen after a 10 minute test ride around town. Maybe with a 70 main or something ridiculous like that. Thanks for the quick responses! |
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Post by endru on Aug 28, 2013 5:58:22 GMT -5
[replyingto=oldchopperguy]oldchopperguy[/replyingto]Good call chopper. The pipe is definitely on the fast road to with all its cosmetic sins, so I'll definitely take your advice and paint it jet black. I think it would look pretty good after that. I think the shops use something like this www.harborfreight.com/12-ton-hydraulic-pipe-bender-32888.html and that would have totally done the job, especially if they torched it. Ah well, it'll all be good in the end. |
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Post by endru on Aug 27, 2013 21:30:04 GMT -5
I just installed a new big valve head. Took it for a test run today and when I got back, I noticed smoke coming out from the engine compartment under the seat while it was idling. I discovered that it was coming from the breather tube on the valve head. It's a significant amount of smoke. Other symptoms which may be related are that it was not idling well during the ride, and I couldn't get any rpm response from adjusting the A/F mixture screw. I have 2 theories. The head may be bad and one of the valves is letting gasses blow by by not seating properly. But that to me wouldn't explain the amount of smoke coming out the hose. The other theory of course is that the rings blew somehow and exhaust is now going past the piston, into the crankcase, back up through the cam chain opening and out the tube. But why suddenly with a new head would the rings blow out? Maybe this is normal for a new head and it will fix itself after it gets broken in. What do you all think?  |
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Post by endru on Aug 27, 2013 21:07:44 GMT -5
Well getting the exhaust pipe straightened was anything but a straightforward job. Jeepsteve - if and when you get your shop to do it, let me know how. I called about 8 different shops, half of which specialized in performance exhausts and none of them said they could do it, something about the pipe being too narrow for their machine. I finally took it in to a place, and begged them to do anything they could. He threw it sideways into a big wide vice and clamped down on the bend. It mostly succeeded in just putting crimps on either side of the bend. But it straightened it just enough that it clears the license plate and fender. The mounting brackets were totally out of alignment at that point. I cut them off at about the midpoint so that I could use another piece of steel as a cripple and jb weld it all together. It didn't hold  So now I'll drill through the cripple and clamp and just bolt them all together. It's not going to look great for now but I just need it to be functional until everything works satisfactorily. So... exhaust pipe saga: done for now.  Thanks again for everybody's help!!  |
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Post by endru on Aug 21, 2013 22:07:31 GMT -5
I was able to make the bend! ;D You can see my handiwork in the picture. I first screwed down the flanged muffler end to a 4x6 board so that I would have something sturdy to grip. Then I traced the angle onto a box so that I could easily check if I was making progress. Then I heated the elbow in question on my stove's gas burner. I was hoping to get it visibly hot (maybe bluish or even red), but after 5 minutes it didn't look any different and I figured it wasn't getting any hotter. I took it out to the garage, laid down some newspaper to protect the garage floor and the pipe... held the board with the pipe attached in both hands, with the very first angle at the beginning of the head pointing down at the ground, then proceeded to simply pound it onto the ground jackhammer-style. I don't know if my description is clear enough, but in any case it worked. It took a lot of force, but eventually I was able to angle it enough (which really wasn't much). It kinked a tiny bit, but I'm not bothered by that. I would show a picture of the header and muffler re-attached to the scoot, but I now have the same problem as jeepsteve: I am considering having my usual shop UNbend the last bend on my header so that the muffler is nearly parallel to the ground. The Znens rear fenders cover nearly all of the shocks. They go pretty low, and can bang on the muffler as it is. My muffler is hitting my rear fender, so I'll have to have the last angle straightened out. I think I'll have a shop do that though, since it's a pretty straightforward job. Tomorrow I'm getting in my new big valve head, so if I can get the exhaust worked out, it'll be happy riding this weekend. Attachments:
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Post by endru on Aug 20, 2013 21:27:14 GMT -5
Hey, great suggestions from some of my favorite people on the forum. Thanks! I think I'll try first heating and bending it by hand, though I'm not optimistic there. If that doesn't work I'll cut it and get it professionally welded back together, which is apparently not supposed to be as expensive as I thought it would be. I like your idea too, oldchopperguy. I'm really impressed with all the creative ways you manage to problem solve. I will go with that if all else fails. I'll post an update when I get it worked out. |
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Post by endru on Aug 19, 2013 22:54:18 GMT -5
That is one option, but it's probably my last at this point. It's hard to find a performance header for less than $35, and who knows if that one would even fit any better. I'm entertaining the idea of cutting it off midway down, rotating the cutoff end a bit to get the right angle, then reattaching it. Would JB Weld work for that, or does the pipe get too hot? I would work it so that the new joint wouldn't be load bearing, it would just need to seal the pipe back up. |
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Post by endru on Aug 19, 2013 21:35:25 GMT -5
So the aftermarket exhaust system I've had hooked up for a few months now angles away from my scooter... you can see for yourself in the picture. From the rear it doesn't look as bad, but it's kind of bush league and the mounting hardware was a bear to get on right. So my proposed solution is to increase the angle of the existing bend in the pipe, but I have no idea how to do it without taking it to a muffler shop and having to pay out the nose. Does anyone have any tips on how to get this done? Attachments:
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Post by endru on Aug 17, 2013 12:56:23 GMT -5
[replyingto=wilds]wilds[/replyingto]Thanks wilds, that's what I was leaning towards myself.
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Post by endru on Aug 14, 2013 20:35:25 GMT -5
I need some advice for my next purchase. I'm currently running with what you see in my signature, plus a stock 19mm carb and stock head. I'm wondering what the next best step would be: a 20mm carb, a 50mm big valve head, or something different? My current carb has the drawback of not having an adjustable clip on the needle. I popped the cap on the A/F screw a while back, and there. It also does not have an accelerator pump, which I think might be helpful, but I haven't heard much about them. I would also need a 40mm air filter, my current one is only 38mm. I feel like a larger carb would perform better with my high-volume setup. The stock head is an EGR head (which isn't truly EGR as we all know) and my exhaust backfires a little unless I plug the inlet hose to that system, so I'd like a non-EGR head. I feel like a larger bore head with larger valves might also perform better. The prices for the two are comparable - about $50 for the head or $50 for the carb plus new filter. I can't find the carb I was looking at before that met my criteria, but here's the link to the head I'm interested in: www.ebay.com/itm/Scooter-High-Performance-Racing-Head-100cc-Big-Bore-Big-Valve-Head-GY6-50cc-/161079743341- Not sure if it's 64 or 69mm valves, I need a 69mm valve head. Thanks in advance for any thoughts and suggestions! |
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Post by endru on Jun 15, 2013 18:54:39 GMT -5
[replyingto=ramblinman]ramblinman[/replyingto]Thanks for the link ramblinman. That did the trick, I found the one I need. Thank you very much! It's a Keihin carb that I have, and both the stock jet and the wrong one I ordered are for Keihin carbs... just 2 different types. |
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Post by endru on Jun 15, 2013 18:00:21 GMT -5
I got my #38 idle jet in the mail today. Went to put it in and it wouldn't fit. The diameter of the threaded part is too wide. If you look at the picture, the new jet is on top. You can see that the diameter of the threaded part on the new jet is wider. I looked on a bunch of different sites, and they all show the same kind/shape as the new idle jet. I guess it serves me right, I should have pulled it out, measured and compared before buying it. Has anyone else had this problem? How do I find an idle jet that fits? Attachments:
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Post by endru on Jun 13, 2013 19:07:25 GMT -5
Be prepared if you get the gears, you'll have to find a machine shop with a major hydraulic press to get the two gears pressed together. Ideally it should only cost about $10 to get them pressed, since it should only take about 5 minutes of their time. But I had a shop try to gouge me and charge $25 bucks.
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Post by endru on Jun 13, 2013 19:00:40 GMT -5
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Post by endru on Jun 12, 2013 21:48:49 GMT -5
I have 7.5 g in rollers from my weight tuning set in right now and the speed has improved like expected, but the skipping is still there. I even got a new exhaust gasket and sealed it with exhaust gasket sealant. It runs pretty smoothly at lower speeds and rpms, but the problem still shows up at higher rpms. So with 7.5 g weights, as soon as I hit about 30 mph, I can hear popping coming out of the air filter and the exhaust, and the scooter skips and hesitates. The most interesting thing was when I took it down a hill, at about 35 mph it was popping and cutting out rapidly, about once every second. It honestly felt like I have a rev limited CDI or something, even though it's the same CDI as before, and I'm pretty sure it wasn't limited back then. So maybe the CDI is malfunctioning. What caused it I don't know, but the issue just feels like a timing issue. An main and 38 idle jet are in the mail, at least now I won't be running quite so lean. |
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, and the scooter ran like crap, stuttering at anything more than 1/4 throttle. So I went up to a 92 and it was much worse, then back down to the 80 since I don't have an 
. I just now went out to do the plug chop and it's definitely lean. 
