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Scooters - 50cc => Agility 50 => Topic started by: The moped learner on September 25, 2014, 12:34:47 AM
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I have replaced EVERYTHING dont ask cdi box or carb change i have changed everything! Does anyone have a 100cc BBK and what is the valves set at for that and is there anything i can do to help it start and run! I have spent days trying to get it to start and no luck PLEASE HELP!😢ðŸ˜
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Valves are .004" or .04mm
I would re check the cam timing that is where most go wrong. W the piston at TDC install the cam so the two holes line up w/ the head, and the big center hole is at TDC.
Te quick way to verify you are at least close is to insert a straw or other soft object (careful here) into the plug hole w/ the valve cover off. At TDC the valves should be closed, and the timing marks should be correct. Exactly correct. Close is a no start. One tooth off in either direction is a no start.
This is a good PDF guide...
http://www.thejunkmanadv.com/uploads/8/4/0/3/8403513/repair_manual_gy6_engine.pdf (http://www.thejunkmanadv.com/uploads/8/4/0/3/8403513/repair_manual_gy6_engine.pdf)
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We redid the cam timing twice and it looked right on and readjusted the valves like 10 times we have been working on it for 3 weeks, 2 weeks trying to get it running
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Have you done a compression test? Have you done ANYTHING to the carb?
You have to remember you now have twice the cc's, and that requires twice the amount of fuel/air mix.
Try a can of starting fliud, and see if it kicks off. DON'T try to run it or force it to run on starting fluid, Just see if it kicks. That will verify the need for larger jets, and perhaps opening up the air box.
My 100cc kit will not run on the normal air box. I had to drill two one inch holes in the back section of the boxes cover, and re-jet both the pilot, and the main.
I believe my pilot is a 40 or 42, and my main is 100 or 105.
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I have re-jet the main to like that amount but not the pilot and i have a pod filter. It will almost start but will not run when shot with starting fluid, it likes to try and start on a little bit past idle but never will run. I have a A9 cam should my exhaust valve be set higher ?
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The bike won't run without a proper pilot jet. The main jet doesn't do anything until well past the half throttle position. This is even more so with a higher lift/duration cam.
Try getting a Torch tip cleaner at Ace hardware or lowes/where ever. It will be faster than waiting for jets.
Find the cleaner that fits into the pilot snugly, and then use the next size up to open it up.
I've never installed an A9 cam so I don;t know the settings for clearance but I would imagine it has to be the same as OEM. You just have a sh** load of air, and almost no fuel in the mix.
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Will try that then i didnt think a pilot jet would make it not start!
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The A9 cam has higher exhaust lift
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Set both valves at .4 ?
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Anyone want a 100cc BBK with the head and jug? I gave up it will never start im tried of working on it i spent $500 on parts and its timed its set to what the valves should be and the pilot is bigger will not even start with starting fluid
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And yes the engine has compression
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There is something simple you are missing due to frustration.
The valves are .004 thousands of an inch OR .04 hundredths of a millimeter. Not .4 of anything.
Check your rocker arm rack. The printing on it should be up-side down when installed correctly. If its not starting w/ starting fluid than you are missing either spark or compression. Those are the the requirements. The subtleties could also be improper valve timing or ignition timing. I would take it back out of the frame. Take it down to bare bones, and let it sit for a few 4-5 days.
Go back at it with the PDF I linked, and follow step by step EXACTLY as laid out. My guess is there is something that you THINK you know but are looking at upside down. Look at it like a retard, and follow step by step. Simple mistakes will make huge head aches.
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My bad i meant .04 mm i thought it looked wrong
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I will see if the valve rocked arm rack is wrong but i don't think it is
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I'm sure it's a simple over site. you just have to go back to the beginning, and review each step.
Are you aligning w/ the timing marks on the flywheel? Did you remove the flywheel at any point?
Did the bike run before you swapped the kit?
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Yes I am aligned with timing and yes I had removed the flywheel why is their something with the flywheel
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It could be the woodruff key did not align properly. It's happed to me more than a few times.
This you can verify w/ a dial mic. or if you are VERY careful to be correct w/ a plastic object/straw in the cylinder thru the plug hole.
It's not the best way due to the side mount plug but it may reveal something. Best bet is to just pull the wheel, and re-do it.
Ive had keys tear off, bend just a few degrees of be so flattened out the wheel can go on in any direction.
Trying to cover all the bases w/ you...
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Ahh ok ill see if it did
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I once had my key fall out and didn't realize it, so the flywheel was just spinning on the shaft. I ended up getting a 125/150 intake manifold and 150cc carb when I put on my 100cc upgrade kit, and the pilot in the 150cc carb works great. I am running a 110 main right now. It wouldn't start with a 38 pilot and ran lean and was hard to start with a 40 pilot. I am not sure what size the included jet is, but it is larger. I also had to play with the needle height for the main jet, and the air/fuel screw adjust is way different ( it wouldn't even start with the number of turns that I was used to ).
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I've been using up-jetted 20mm carbs but you are 100% correct Redun... The 24mm (150 cc) carbs work just fine
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But it won't start on starting fluid
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All that means is either the compression is low due to valve timing or the ignition timing is off.
Get a compression tester, and a new spark plug. I've had bad plugs right out of the box.
If you have good spark, and starting fluid, it has no choice except to start unless one of the other issues is present.
Do yourself a favor too. Try the engine w/ the OEM cam. I don't trust China performance parts as much as some others do.
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We had it runny with the big valves but ran like crap because it was runny lean but after we put the stock size valve back on it won't run
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Compression test...
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Havnt done that but what should it be at?
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Anything over 120psi. 135 is normal.
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But did you hear i had it runny with the big valves but after i had to changed to the small stock valves it would not start
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Did the bike run before you put on the kit?
There is no reason it will not run on either hear if both heads are good.
In fact I always use the OEM head because it has a smaller combustion chamber, and higher compression.
You have to help me/help you. You need a compression test to see what is going on.
OR
Take it all back apart, and go step by step w/ the installation instructions I linked you to.
I can't guess what is going on unless you go step by step.
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No it had a 80cc BBK but the oil ring near the rod a peace broke off so i had to get a new kit
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Ill try and post the compression test soon
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That may be why the old small valve head is not working. May be a piece of the ring scored the valve, and it has no compression. Just a guess...
Did you get the 64 or 69mm valve kit?
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64mm but if i adjust the in tank valve so its open it will spend fast but if i close it it well barely turn over
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what do you mean? The valves should never be adjusted open.
I'm getting very confused here...
Re -read this thread, and try to do the things I asked, like follow the directions for the install. Twisting valves, and pulling screws won't fix it.
You have to be methodical to know where you went wrong. Shot guns are for opening doors. .45's are for doing the work inside.
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Open? I have done every thing you have said. Other than a comp test. I mean i twist the adjuster till the valve is open so i can see how it sounds then i adjust it till its dosnt open as much then turn it over
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The valve should never be adjusted that tight or in an open position. It WILL collide with the piston, and bend the valve.
Please do a compression test. It may just lead to the answer.
If you have the other head... Spray or pour some carb cleaner into each one of the ports. One at a time. You want to see if the carb clean will leak out thru the valve. That will tell if you have a bad head/bent valve.
Even the slightest leak will prevent the engine from running.
I'm gonna start drinking again.
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Ok ill see what it says
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Well I don't have the right size for the spark plug hole all i have is size whys is for a ford 302 engine so the test will have to wait
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I forgot these things need adapters...
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I just might scrap the 100cc BBK and go for a 80cc again
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It's not the kit unless there is a defect that you did not catch. That's why I said to start from scratch.
You might have put the rings in upside down, the end gap could be wrong, the piston could be too loose in the cylinder, the chain tensioner for the cam could be jammed, the head gasket could be leaking, valves could be bent or have damaged seats.
there are too many things to list. One step at a time.
Get a feeler gauge, and start with the piston fit in the bore with no rings installed. It should bee between .002, and .0035" everywhere in the bore. End gap should be no larger than .004" anywhere in the bore.
I have seen brand new cylinders that have a reverse hourglass effect in the middle of the bore. Use the piston to square the rings to measure this.
It's easier to speculate, and type all day than it is to do this right, and that says alot because putting one of these together is about the easiest of all engines. One cylinder/piston to measure.
I am in the middle of building three engines right now.
One, '69 Triumph
Two, QMB 139
Three, 350 Chevy marine HP
I always measure everything, and plasti-gauge all the bearings. That process takes longer than assembly. As a matter of fact I am weighing/balancing all the moving parts in the Triumph because that one is mine, and I want a bad ass engine that will last at least ten more years before another rebuild. It's already 45 years old.
Set your mind to doing this right, and you can get it done. You wasted more time already than it would have taken to dig up the ore/forge the parts/build the engine. I'm busting your balls because I know how easy it is to build this engine. You don't see it that way, YET.
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Well i think ill be going back to the 80cc BBK the 100cc BBK was something i knew i would have problems with
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Im making some money so $50 out of a pay check is nothing
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The kits are exactly the same but if you feel better about another kit... It's all good.
Please keep us informed as to how you make out.
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I will i never had problems with the 80cc BBK other than the lip right above the oil ring where the piston rod goes throw a peace came off and scored up the wall bad
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Cheap cast pistons. You'll get one in fourty that wont last.
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Well got the 80cc BBK so now its time to install it wish me luck
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Best to ya!