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Post by bullet28027 on Nov 12, 2009 22:49:53 GMT -5
Hello Fellow Rebels, New Cadet here, my name is Haywood, I look forward to working up through the ranks, and getting to know you guys and gals.
A little about my scoot: X-treme XM150, 2900 chinaomiles, says Jonway in seat barrel tag, Mods: exhaust straight through design, coil, stage 1 cdi, Uni sock filter, new KF 24 mm carb, all new goodyear fuel and vacuum lines, new fuel filter, fuel cut off valve.
Current setup: valves adjusted, needle in lowest position, 107.5 main jet, 35 idle jet, 12.8 gram factory rollers, new gates powerlink belt 843/30/20, factory clutch. fresh oil, and gear oil change, new ngk cr7hsa plug, bypassed the new mikuni fuel pump, as tank is higher than carb.
Problem: down on power, max rpm's 5000 under load, 7800 rpm's on stand. After reading Leo's post "possible BREAKTHROUGH for carburetion" I realized we had the same symptoms, cackling, bogging. I removed the air filter and the modified hose I made from a radiator hose, changed the jet to the 107.5 and it picked up to the 7800 rpm's on the stand, with no filter at all, put filter directly on carb and it decreased to 6200 rpm's and the cackling and bogging returned. Test run with my 210lbs would not break 5000 rpm's with no filter, should I experminent with jets with the filter on? Could being off just a little on the jet cause loss of rpm's, or should I start looking at the clutch. It feels like pulling out of your driveway in fourth gear.
Any help to get me in the right direction is gratly appreciated, Haywood
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Post by Rebel on Nov 12, 2009 23:10:36 GMT -5
Welcome
You asked about the air cleaner, is it clean? Have you washed it out and do you use oil on it?
Do you have the original belt on it?
Are the rollers the originals?
You put a new carb on it, how was it doing on the old carb, was it running fine? no "crackling or bogging"? and did you just put the exhaust on? It is always best to do one mod at a time, get it going good on that then go to the next mod. What were the size of the jets on the old carb?
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Post by bullet28027 on Nov 12, 2009 23:46:06 GMT -5
filter is clean no oil, paved roads only, new gates belt on, rollers are factory 12.8 grams, old carb broke needle retainer no way to fix so I jbought a new one, factory jetting was 101 or 103. exhaust is pretty new, but it was bought because the old one was making alot of noise on the inside. bought the new carb because the old carb broke the retainer on the jet needle.
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Post by Rebel on Nov 13, 2009 2:33:16 GMT -5
Needle is set to lowest position, that will make it run as rich as possible, have you tried it in any other position? You already have a larger jet then it is set to run as rich as possible. Toss the fact that the carb is rich and then a filter added makes it start running worse. I'm thinking you need to lean it out some. Now that and a buck might buy you a cup of coffee at Denny's. Have you run it and then checked the plug for carbon deposits?
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Post by jct842 on Nov 13, 2009 21:48:09 GMT -5
don't over look the fuel pump. my carino was running out of gas after 15-20 sec at WOT. a mikuni cured it. john
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Post by oldchopperguy on Nov 14, 2009 15:00:23 GMT -5
Hey bullet28027,You do have the same problem I had! The one big difference is that your scoot used a fuel pump, and mine is strictly gravity-feed. As a side note, my engine seems to run as usual (good OR bad) as long as there's fuel in the float bowl. Poor fuel delivery to the carb certainly makes it quit when the bowl runs dry, but I have not experienced erratic running from poor fuel flow to the carb (which I did have with the stock petcock).Now, assuming your trouble is NOT the lack of fuel pump, you still have the same problem as I did (nearly EXACTLY). I found the MOST critical element to be the air-filter setup. I would suggest doing all tuning without any filter on the carb, as you are now, THEN work backwards, incorporating a UNI filter with no intake runner after it's running right. (Please note: the catback brace over the sock filter will try to pull the filter off while driving.) I stretched the UNI coil spring forward and worked it over the mouth of the carb before attaching the clamp. So far so good! If that fails me, I'll reverse the intake to put the carb facing forward, as some others have done. That involves considerable work, and is a last resort however... My replacement carb (Mikuni 24 mm direct replacement type) came with a 42.5 idle jet and if I recall, a 112 main. This runs great with my needle modified. I tried MANY different jets during my "tribulation" LOL... and none made a major difference in actual running. You do want a good setup though, to protect your engine from too-lean, and get good gas mileage. Some GY6 engines may respond a lot to jet changes, but mine did not. (The stock Chinese carb which did go bad, had a 103 main jet, and still did not show too-lean burning on the plug.) But it certainly WAS somewhat too lean, and that will rob top-end revs. I never did get the engine to lose that "leaving the driveway in high gear" syndrome you have, until i modified the carb needle to go 2 full notches richer than stock! (Higher than the highest stock position) I can't begin to explain why that is, but getting the needle even higher (richer) than "max" did the trick on mine. The higher the needle went, the smoother the takeoff from a stop. I have a distinct feeling that with a better exhaust, I may need to cut yet another higher notch on the needle! Here are pix of the modification.I tend to think this is a rare situation, but NOTHING else would get my scooter moving without starving for fuel. Each one is SO different! I realize yours could be just the opposite. I believe we both have the same no-rev-limit CDI, and that made a noticeable difference on mine, as did the better coil. Idle speed increased over 1,000 rpm with just those changes, and had to be adjusted for. The high-end "cackling" and loss of power however still remained, and only the needle mods and air-filter diddling ever removed that problem. Final adjusting of the idle-air screw helped a little, but jetting changes brought little difference. Getting the needle so it begins lifting with just a little throttle was a BIGGIE. I don't see why that should increase top rpm though... only startup acceleration. I hate to admit it, but I'm still running the original spark plug (it WILL get replaced soon...) and stock exhaust. On the stand, the engine will now shoot past 8,300 rpm and I quickly close the throttle. No use "testing" top rpm with no load. I weigh about 255 (shame on me!) and the scoot will accelerate smoothly up to 8,200 rpm, which is about 53 mph. It's overall driveability is excellent now, and for lower cruising rpm, and a little more top speed, a better variator is now needed. One's coming from Santa... From what jrryan on ScootDawg has told me, the Prodigy variator from Carlos in Taiwan is a true MIRACLE WORKER! What's working for me may, or may not work for you, but we seem to have the same problems. Please feel free to PM me if you wish, and I'll surely do my best to "talk shop" about this. I'll be glad to give you my phone number if you want to talk about it personally. Nothing's more irritating than having a nice little scoot that just won't go! Hope I may have been of some help! I'm firmly convinced these engines vary TREMENDOUSLY in their running characteristics. Some run strong out of the box, some don't. Some like ours, may run OK for a couple thousand miles, THEN change attitude completely! You and I aren't the first troopers to experience that... No explanation for that, but they can be made right with patience. LOTS of patience...With both my Wife and me aboard (see the little avatar pic) it will STILL break over 8,000 rpm and over 50 mph, with virtually no difference in acceleration. That's carrying a 400+ lb load. So I'm thinking a little "rich" on both the needle, and the jets gives a pretty good safety cushion for the engine. My gas mileage has dropped from 95 mpg to around 75 mpg, but that is a small price to pay for good running with a load. Ride safe!Leo in Texas
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Post by bullet28027 on Nov 14, 2009 19:05:18 GMT -5
Thanks Leo, I went up to a 130 main jet today. I tried a 115, a 125, and a 127.5 and it still shows no signs of running rich, with the air filter off it would go up to 7500 rpm's on the stand, put the filter on and it drops to 6000 rpm's and the cackling returns. Also I adjusted my valves today, .004'' intake and .005'' exhaust. I had them set at .04mm. not much help, it just wont go, test rides today max rpm's around 5000. I think I will try going down on the jet and all the way up on the needle maybe a 115 jet. i'll keep ya posted. Oh by the way nice work on that custom needle!
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Post by oldchopperguy on Nov 15, 2009 2:45:55 GMT -5
Bullet28027,
I forgot to mention I have also removed ALL the weird emissions plumbing on the head. Now mine may be totally different from yours, but mine had a fitting on the head, connected to a heavy rubber hose, connected to some other apparatus. This mess has a name, which escapes me right now. Many GY6's have similar units. Some are different, but all are potential driveability problems. At least in Texas, this stuff is NOT required by law, and is just trouble waiting to happen.
I blocked off the head fitting with an aluminum plate under the hose fitting, and made sure any extra connections/vacuum ports, hoses, etc. were GONE. This MAY or may not be part of the total fix. It depends on your individual engine.
Thanks for the compliments on the needle mods! I did it on a small lathe, but you can do it just as well by chucking the needle in a drill, and using a Dremel tool with thin cutoff wheel freehand against the spinning needle. It honestly DID make a VERY BIG difference, but again, each engine is so different in running characteristics.
I'd think your jet choices would be just fine for now. Valves should be OK too. Mine are at .004" both intake and exhaust (set there from the factory, and have not changed).
I know the discouragement of that pesky air-filter killing the performance! On mine, the UNI sock with no intake runner doesn't make a noticeable drop in rpm. But, even a short extension, even with NO filter on it does. These things are SO sensitive to filter setups.
On yours, I'd still try to be absolutely sure the absense of a fuel-pump isn't causing a problem. I doubt it is, but you never know. From there, I'd try removing any and all "emissions" pieces, and block off any openings. It's part of my own fix which I had forgotten about. In the process, be absolutely SURE there are no open vacuum ports, or loose-fitting hoses. A vacuum leak can cause similar problems. Also be sure the carb is seated well into the intake manifold and clamped tight, and be sure the intake manifold is fastened well onto the head, with no cracks or air leaks in it. (You can check for cracks/leaks in the manifold by a quick spray of starting fluid around the manifold while the engine's running). If it speeds up, it's sucking starting fliud in through a leak. Be careful with that stuff, it's quite flammable! I keep a fire extinguisher handy as a precaution.
All the MISERY will be forgotten the first time it shoots past 8,000 revs on the stand, and hauls your butt past 50 on the street!
All my VERY BEST wishes on this one! I REALLY know EXACTLY how you feel! Been there, done that, got the T-shirt! Your scoot must have been made by the same guys who made mine!
Sincerely,
Leo in Texas
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Post by kuzikood on Nov 15, 2009 11:06:04 GMT -5
doublecheck valve springs make sure they arent crushed ,broken etc , lower the needle to the next to lowest position and try it. it sounds alot like what mine was doin with a broken outer valve spring on the intake valve try that if it isnt that theres a few more ideas bumpin around in my noggin
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Post by oldchopperguy on Nov 15, 2009 20:38:44 GMT -5
Kuzikood has a good idea there!
Never having had valve-spring trouble, I had not thought of that. Certainly a faulty valve-spring could cause the trouble. If that's the trouble, it would be a relatively easy fix!
Happy wrenching!
Leo
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Post by bullet28027 on Nov 15, 2009 21:32:26 GMT -5
I will check it out and keep ya posted, by the way I only have one vacuum line from the intake to the carb, and the one breather hose from the valve cover that i should make a catch for but I don't see any oil coming out of it so that is on the back burner. I had to order an adapter for my new compression tester to go to 10mm, it will be a couple of days before I can do a compression test. what is the compression suppose to be? Thanks Leo, and Kuzi for helping me out.
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Post by oldchopperguy on Nov 16, 2009 14:20:02 GMT -5
At least you're not encumbered with a load of emissions plumbing! That eliminates several potential problems!
I don't know what the compression should be on these, but several of the more expert troops do. I'm sure they will come to your rescue! I'm not by any means expert on these engines, but have now done enough trial and error maintenance to find numerous "bad habits" they seem to harbor...
The "petering out" at high rpm, and extreme sensitivity to air intake setups does not seem to be universal... BUT... yours and mine certainly suffer from it! Looks like that phenomenon could be a completely separate subject of study for those who have scoots with the same symptoms!
As "Red Green" used to say: "...We're all in this thing together..."
Always happy to pass on fixes that did, or did not work for me!
Stay safe!
Leo
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Post by rapidjim on Nov 17, 2009 9:58:55 GMT -5
Compression should be over 150PSI.
Jim
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Post by bullet28027 on Nov 19, 2009 16:12:31 GMT -5
Tested the compression today, it was 100 psi, going to go take a look at the valve springs, I will keep ya posted.
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Post by Rebel on Nov 19, 2009 16:28:17 GMT -5
be sure to double check the valve adjustment too.
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