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 Author | Topic: Need HELP (Read 602 times) |
lampk
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|  | Need HELP
« Thread Started on Oct 5, 2011, 2:28pm » | |
OK were to start-I have a adly thunderbike with a 1E40QMB engine.Last summer i installed a 70cc big bore kit and got approx 3000 miles on it with no problems then last week it blow a hole in the piston.
So this week i tore it apart and put another piston and head on it but i cannot get it to start. When i feel for compression it feels like it is sucking in not pushing out? when i installed the piston i put the arrow facing down towards the exhast port.
any help or info would be great!
kevin
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yoshidawg
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« Reply #1 on Oct 7, 2011, 9:33pm » | |
Only suggestion is try a compression gauge on it. I think I would take it apart and check the rings and then re-install it. You sure that piston fits tight?
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skuttadawg
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| | Re: Need HELP
« Reply #2 on Oct 7, 2011, 9:41pm » | |
Check the valves to see if opening and closing all the way . Scooters run lean and when you mod it and do not upjet the carb you can be too lean and burn up a piston . Somtimes a shim aka spacer or extra base gasket is required so valves do not hit the piston . With a BBK youi must use PREMIUM gas only never use 87 . I cracked a piston in a 72cc and did not get to run all of the 87 gas out ,it had to be drained and refuled with premium . A BBK with stock head has higher compression than stock and small combustion chamber you must use premium or it will spark knock and fry a piston . MBE Motorsports has forged pistons which are much stronger than cast and last longer
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| | Re: Need HELP
« Reply #3 on Oct 7, 2011, 9:54pm » | |
No Valves it's a 2 stroke.
How are you checking for compression?
Take the plug out and stick your finger in the hole and hold the throttle wide open and crank it. IF it has DECENT COMPRESSION it will blow your finger out of the Spark Plug Hole.
If Not then your install did not go well, did you put in new rings and offset the ring gaps correctly.
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lampk
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« Reply #4 on Nov 2, 2011, 3:00pm » | |
Ok still at it ,If i had hair i would have pulled it out by now.
Still have a scoot that wont run not even a misfire cough sputter nothing?
Iam woundering if the new cyl head is incorect and causing the intake and exhuase stroke to be off with timming?i measured both the old 72cc bbk and the new 72c bbk.Both cyl are the same length but exhaust and intake are not.The new head intake is 2mm closer to the top of the cyl and the exhaust is 3mm closer?
any sugg would be helpfull !!
kevin
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| | Re: Need HELP
« Reply #5 on Nov 2, 2011, 4:22pm » | |
Now I'm confused. If the head has an intake and exhaust, are you sure this is a two-stroke? A 2T cylinder head is usually just a combustion chamber and a place for the spark plug. A 4T would have intake and exhaust ports and a cam, rocker assembly, valve cover, etc...
If you mean there are ports inside of the cylinder and they are closer to the top of the cylinder, that just means they'll stay open longer. Pretty typical of performance cylinders for 2T engines.
For a no start, first verify that you have all of the following... fuel, spark, compression.
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gregw
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« Reply #6 on Nov 2, 2011, 8:43pm » | |
If the intake and port windows in your cylinder are closer to the top, than it is designed to run at a higher rpm than your old motor. Have you checked for spark? Are you positive you don't have "valves" built into your cylinder head? If so, it's a four stroke.
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jimh
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| | Re: Need HELP
« Reply #7 on Nov 2, 2011, 9:41pm » | |
Oct 7, 2011, 9:41pm, skuttadawg wrote:| Check the valves to see if opening and closing all the way . Scooters run lean and when you mod it and do not upjet the carb you can be too lean and burn up a piston . Somtimes a shim aka spacer or extra base gasket is required so valves do not hit the piston . With a BBK youi must use PREMIUM gas only never use 87 . I cracked a piston in a 72cc and did not get to run all of the 87 gas out ,it had to be drained and refuled with premium . A BBK with stock head has higher compression than stock and small combustion chamber you must use premium or it will spark knock and fry a piston . MBE Motorsports has forged pistons which are much stronger than cast and last longer |
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Please! Really?
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rob98801
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« Reply #8 on Nov 3, 2011, 10:18am » | |
If I could back up just a little.
Do you have a good spark? (forget the timing for the time being), IS there a good spark, a Bright blue, Snapping spark. (You DID replace the spark plug)
Do you have compression? As others have said, At the least plug the spark plug hole with your finger and turn the engine over, at the best use a compression gauge.
And last but not least, Fuel. You do have fuel getting to the chamber?
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lampk
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« Reply #9 on Nov 3, 2011, 8:44pm » | |
Aloha
thanks for the advise, yes i have a new plug and plenty of spark.
It feels like lots of compression holding my finger over the plug hole-have on order a compression tester to get more of an accurate compression.I have tried dipping the spark plug in gas and also tried putting a little in the cyylinder with no luck no a pop or backfire nothing?I will have a better idea once the compression tester arrives.If all else fails i will skip the priming of the cylinder head and just prime the entire scoot-getting close to that already lol.
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rob98801
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« Reply #10 on Nov 3, 2011, 9:05pm » | |
Hang in there with me. OK, so you have fuel, compression, and spark.
When the burn out happened did the engine freeze or seize up at anytime?
When you replaced the cyclinder, piston, rings and head you also replaced the head gasket and cyclinder gasket? You cross patterned when tighting the head bolts?
Rob
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lampk
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| | Re: Need HELP
« Reply #11 on Nov 4, 2011, 1:14pm » | |
Aloha
Yes i replaced the cyl,head and piston.Installed the new gaskets and tighten in a cross pattern.Strange part is that the compression feels the same on the down stroke-what i mean by this is the suction feels as strong as the compression cycle?
When i crank the engine over with no throttle and hold my hand over the carb it feels like air is being pushed out and dont feel suction untill wot?Iam just stumped?
kev
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lampk
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« Reply #12 on Nov 4, 2011, 1:21pm » | |
Sorry forgot to add that it did not seize when the piston went.
kevin
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gregw
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« Reply #13 on Nov 5, 2011, 8:39pm » | |
lampk, if your finger is over the spark plug hole, and you're cranking it over, it will have just as much suction as compression. That is because it is a two stroke. A compression gauge will tell you differant though, because the gauge won't allow air to escape like your finger will.
And with the engine not running (sparking and firing), you won't notice much differance in vacuum between open and closed throttle while cranking it because the cranking rpm is so slow. A four stroke will take a more noticable gulp every second revolution.
You shouldn't need to wet your plug, or put fuel in your cylinder to get your scoot running. In fact, you could flood it, then you'll have a heck of a time getting it running. Even though Ether is not good for two strokes, I would shoot a short burst into your carb at WOT while cranking it, and see if it'll run. If it still won't fire, and your spark plug is dry after trying the ether burst, I don't know what to tell you... good luck!
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lampk
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| | Re: Need HELP
« Reply #14 on Nov 8, 2011, 4:21pm » | |
Aloha
ok did a compression test today ,115 psi on wot.It is low but should have enough to start?
any advice would be great?
kevin
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lampk
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« Reply #15 on Nov 8, 2011, 4:40pm » | |
Aloha
just did another compression test with fully charged batt and it came out as 125 psi.When turning engine over i can feel a lot of sucksion from the carb. Tried the spraying started fluid in the carb -still nothing so i took the plug out and it is dry?whats next?reed valves?
any help would be great.
thanks
kevin
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lampk
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« Reply #16 on Nov 8, 2011, 5:18pm » | |
Aloha
had the reeds out ,they looked ok (metal) were not broken.This may seem odd but can the be put back in backward?One of the for small bolts that hold the houseing on is stripped and will only tighten finger tight so i put on some gassket glue.could this be the cause? how can i check if it is sealed ok?
thanks
kevin
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rob98801
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« Reply #17 on Nov 10, 2011, 10:51am » | |
Kevin
As to the stripped bolt, if it is a bolt replace it, if it is a stud that is stripped replace it, if it is the treads in the body of the case, repair with a Helicoil insert.
As to the engine NOT firing I am completely lost given the fact that you have fuel, compression, and spark.
I think you have missed something. For example a blown key on the fly wheel taking the timing south. There is something there that is hiding the problem, I would suggest that another sets of hands and eyes would be in order at this time.
(As the temp outside my house is right at 28* this AM and I note you are on the islands and I could be pushed into traveling at a lower than my normal imperial first class Accommodations. to help out a fellow scoot.) Sorry got off subject.
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Rob
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lampk
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« Reply #18 on Nov 10, 2011, 1:30pm » | |
Aloha
Thanks for all those who took time to help,so here is an update.
First got the stripped bolt fixed,took the reeds out and flipped them over(someone told me to try this)Cleaned the carb out with carb cleaner put everything back and THE DARN THING ACTUALY
FIRED UP !!!It seems to run ok but now i will have to rejet so that it doesnt run lean again and find myself in the same spot a year from now LOL.
once again thanks for all the help !!
Kevin
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rob98801
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« Reply #19 on Nov 10, 2011, 4:32pm » | |
Damm and I already started to pack, oh well, GREAT to hear you got it running enjoy....
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Rob
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lampk
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« Reply #20 on Nov 10, 2011, 5:05pm » | |
Aloha
darn bags were packed lol,been raining like crazy here for the past week,but i did manage to take it out for a drive-lacks power big time so not all is cured yet.It bogs down and i have tried to adjust the carb with no luck.I have an #85 main jet that i b umped up to #90 and #95 with no change?Maybe its time for some new reeds?
It is gutless compared to the last 72cc kit .
kevin
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