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Post by katt on Aug 22, 2018 13:35:25 GMT -5
Well torque on head bolts and oil problems i don't see a relationship.
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Post by AtariGuy on Aug 23, 2018 0:49:36 GMT -5
Well torque on head bolts and oil problems i don't see a relationship. 0 the head nuts hold the rocker arms in place, but the oil passage follows the head bolt. If a lightly torqued headnut comes out, it compromises the oil passage |
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ratdog
Scoot Enthusiast
Posts: 342
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Post by ratdog on Aug 23, 2018 2:53:53 GMT -5
I'm thinking what he may mean is that lets say you didn't use an X pattern when tightening the head bolts and tightened one sit real tight first, then tightening the other side might not bring the head back to flush. IMHO that would be more likely to cause you to blow a head gasket then have an oiling problem, but there is a good chance it could cause an oil leak.
I'll add my 2 cents worth on break in.
First, while you are putting the bike back together, get and use assembly lube. Most of the install vids I watch leave this very important step out. don't forget to slobber it all over the cam lobes and rockers as well.
IMHO the most important thing on first startup is to keep the RPMs up. I have seen too many vids where on first startup they let the engine idle for 5 or 10 min. These little engines don't pump a lot of oil at low rpms. I set my throttle stop at about 3000rpms for the first 5 hours or so.
How this is advice based on the old "if you want them fast, break them in fast" school. I always run at different speeds and loads (never a long consent speed) but throw in a lot of WOT blasts up to the mid 30s.
As far as break in mileage, i don't worry about miles, I am more concerned with hours. this has to do with the CVT trans. the CVT tries to keep your RPMs up int the 7000 rpm area. so if your going slow and not racking up a lot of miles, you are still logging a lot of spinning on that engine
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Post by V90Performance on Aug 26, 2018 19:14:06 GMT -5
A year later, 5000 miles on my Naraku 52.4mm bbk. Which crank did you used? Sorry for the late response, I am currently using the stock crank. |
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Post by KSR Moto on Aug 27, 2018 8:02:39 GMT -5
Which crank did you used? Sorry for the late response, I am currently using the stock crank. 52.4 on a stock crank and it hasnt failed shortly, that is awesome |
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Post by katt on Sept 2, 2018 2:17:35 GMT -5
Installed 50mm (80cc) BBK and my compression currently is 180 psi because i have standard 39mm (49cc) head,
Very rough estimate 180 divided by 14.7 = compression 12.2:1 when QMB139 made for 10.5:1
This creates more pressure on crankshaft bearings?  |
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Post by dexameth on Sept 2, 2018 6:42:10 GMT -5
The Kymco Agility service manual calls for 200psi on the stock motor, my stroker 94cc is 205 psi (was... Haven't checked since built) but yes more power from the high compression will lead to more heat in the chamber and more pressure on the bearings. Might even get blowby past the rings and maybe even the valves if they don't have a perfect seal.
Make sure your piston isn't contacting the head, I've seen that happen way too often. Polini and Airsal both make a 50mm kit that is tested and designed around the stock head.
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Post by cristian on Oct 28, 2018 4:02:06 GMT -5
Hi, I am a beginner so please treat me gently? What would actually break in case of a 50mm cylinder? The cylinder itself? The cranckshaft? I am asking because I want to buy spare parts to have them just in case. Usually, it's difficult to find parts where I leave. So, I need to order them abroad and it takes 1 week or more to receive them.
I am currently running a 50mm airsal aluminum kit, a 19 mm carb and a malossi multivar 2000 with 6 gram rollers.
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Post by lunatuck on Sept 25, 2019 8:55:41 GMT -5
Hi, I am a beginner so please treat me gently? What would actually break in case of a 50mm cylinder? The cylinder itself? The cranckshaft? I am asking because I want to buy spare parts to have them just in case. Usually, it's difficult to find parts where I leave. So, I need to order them abroad and it takes 1 week or more to receive them. I am currently running a 50mm airsal aluminum kit, a 19 mm carb and a malossi multivar 2000 with 6 gram rollers. The most common seem to be warped heads and broken crank. I believe a lot of the issues are caused by using the incorrect head/valves with the BBK.
Lol. Just realized that was a year old.
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Post by smooch on Oct 16, 2019 10:11:33 GMT -5
I have a 50cc Taotao with a BBK. 50mm piston, big valve head, A9 cam, no rev CDI, performance exhaust and 40/17 final and a 20mm CVK carb.The CVT is banging around. It was hitting 50mph now it struggles to do 40mph. It's starting very hard so I did a valve adjustment and still starting hard. Could my timing chain have jumped a tooth? Carburetor problem? I installed the 49/17 last season? They are pre pressed finals?
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Post by scooterted on Oct 16, 2019 11:33:20 GMT -5
I have a 50cc Taotao with a BBK. 50mm piston, big valve head, A9 cam, no rev CDI, performance exhaust and 40/17 final and a 20mm CVK carb.The CVT is banging around. It was hitting 50mph now it struggles to do 40mph. It's starting very hard so I did a valve adjustment and still starting hard. Could my timing chain have jumped a tooth? Carburetor problem? I installed the 49/17 last season? They are pre pressed finals? Youll have better luck starting a new thread in the 49cc 4 stroke troubleshooting forum. As for as your issues. Since the cvt is clunking, open it up and have a look. Hard starting, i would spray the passages out in the carb, have a look at your idle mixture and do a compression test. Also, the performance cdis advamce timing so much it can be hard to start. |
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Post by smooch on Oct 22, 2019 15:26:46 GMT -5
Thanks bro I got it running better. I put the pd19j back on with a 34 slow jet and a 88 main jet. The idle keeps changing just need to idle it down a bit so the clutch isn't engaging. That's why my cvt was bumping!! Yes I did put a BBK with 50mm piston, 23mm int 20mm ex head, A9 cam etc!! I just think it may be time for a rebuild?
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Post by smooch on Feb 14, 2020 22:00:27 GMT -5
Big end failure. I have since replaced the CS and upgraded to the airsal piston. Which IIRC is lighter than the standard 50mm, also domed a big plus. |
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Post by smooch on Feb 14, 2020 22:18:04 GMT -5
I have a BBK 50mm piston and every other performance upgrade. My scooter turns over strong but won't fire. I put a no rev limit CDI in also. Could the no rev limit CDI be advancing my timing so it won't start up. I have it running good when I can start it. When it does start and has been running for a while it will start right up like it should. My valves are adjusted every 600 miles give or take a few miles. So I know that's not the problem.
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Post by smooch on Feb 14, 2020 22:21:15 GMT -5
I wonder if it would be possible to lighten the 50mm piston a bit? You could drill a series of holes below the piston rings on the skirt. It would not make it much lighter and would make it a bit weaker but, you could do it. Bill |
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