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Post by ksaun123 on Jan 8, 2015 1:38:54 GMT -5
I have a 1P52QMI engine that i upgraded to a 150cc. Bought new head, cylinder, gaskets, and piston kit. Noticed over time It started loosing compression, even stopped sucking in gas from the floor tank. Wondering if the cylinder cutout is too big. I have a odd gap between the piston and the cylinder. (I only got the cylinder for $20 anyway). Changed the piston rings after 0 miles and still same problem. Oil pump works fine too. Is this normal? If so, how can I fix the compression? I also did the finger in spark plug thing and it didn't push my finger out. Wondering if I should have got the 149cm^3 cylinder instead... I set the valves to 0.05 intake and 0.06 exhaust i58.tinypic.com/11j7sc9.jpg JR, alleyoop, Doug, JerryScript, skuttadawg, |
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Post by JR on Jan 8, 2015 8:01:52 GMT -5
Have you actually checked the valves to see if they are seating well? Even with the gaps right if you have a valve blowing by you'll have no compression to speak of?
Take the head and sit it down on a flat spot with the sparkplug in tightly and just pour the whole valve seat area with a thin oil or WD-40 and wait to see if the oil stays put or seeps out onto the surface below. If it does then you need to remove the valves and reseat them with valve grinding compound if the valves do not have a bad burned spot on them.
I bought a brand new head once with badly seated valves.
JR
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Post by geh3333 on Jan 8, 2015 17:22:53 GMT -5
I have a 1P52QMI engine that i upgraded to a 150cc. Bought new head, cylinder, gaskets, and piston kit. Noticed over time It started loosing compression, even stopped sucking in gas from the floor tank. Wondering if the cylinder cutout is too big. I have a odd gap between the piston and the cylinder. (I only got the cylinder for $20 anyway). Changed the piston rings after 0 miles and still same problem. Oil pump works fine too. Is this normal? If so, how can I fix the compression? I also did the finger in spark plug thing and it didn't push my finger out. Wondering if I should have got the 149cm^3 cylinder instead... I set the valves to 0.05 intake and 0.06 exhaust i58.tinypic.com/11j7sc9.jpg JR, alleyoop, Doug, JerryScript, skuttadawg, When u say u have an odd gap between the piston and the cylinder , do u mean the piston is able to move side to side in the cylinder ? |
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Post by geh3333 on Jan 8, 2015 17:24:44 GMT -5
The pic u posted seems to show too much of a gap between the piston and cylinder for sure .
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Post by ksaun123 on Jan 8, 2015 17:54:30 GMT -5
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Post by ksaun123 on Jan 8, 2015 18:03:09 GMT -5
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Post by geh3333 on Jan 8, 2015 18:45:41 GMT -5
U r going to have some play in the piston ,because the rings may allow the piston itself to slightly move ",since they are loose within the piston ". however it should not be much. It just looks like a lot of room between the piston and the cylinder wall.
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Post by jerseyboy on Jan 8, 2015 19:22:03 GMT -5
Put it at TDC and do a leak down test,,very easy to do and it will tell you exactly where you are leaking...
Hiss in carb= intake valve
Hiss in exhaust pipe=you got it,,,exhaust valve
Hiss in oil filler hole=yup...rings/piston/scored jug...
I made one out of a HF compression tester and an old air regulator valve,,very easy...
Hope you get it figured out man!!
Tom
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Post by ksaun123 on Jan 8, 2015 20:03:32 GMT -5
Does anyone think a 58.5 piston would fit in there?  |
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Post by jerseyboy on Jan 8, 2015 20:38:40 GMT -5
Not in a stock 57 jug,,nope..measure your bore at top bottom and all four sides,,see if the numbers jive..Ill measure my stock bore tomorrow for ya..pretty sure its 57mm on the $$.
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Post by geh3333 on Jan 8, 2015 20:41:36 GMT -5
Does anyone think a 58.5 piston would fit in there? Will it fit ? Maybe , but will it work ? I wouldn't do it . however if I had and extra engine with an extra few bucks to throw around I'd like to try it , just for the heck of it . the thing is that there is enough room for the piston to fit in the jug but the rings would have to be worked a little and even then they are gonna be tight . I can't say for sure what would happen because I've never tried it and I do not know anyone who has . |
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Post by geh3333 on Jan 8, 2015 20:46:14 GMT -5
Not in a stock 57 jug,,nope..measure your bore at top bottom and all four sides,,see if the numbers jive..Ill measure my stock bore tomorrow for ya..pretty sure its 57mm on the $$. Is the jug 57mm or is the piston 57mm ? If the jug is 57 then the piston is smaller the same with if the 58.5 is the jug size then the piston is smaller . so I'd say it may fit but may not work . Ill measure my stock piston real quick |
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Post by ksaun123 on Jan 8, 2015 20:46:46 GMT -5
Appreciate the feedback. By the way is anybody been getting packages lost by usps lately?
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Post by geh3333 on Jan 8, 2015 20:54:25 GMT -5
Man I just measured the piston and jug , I forgot how tight the piston is in the jug even without the rings, jersey is right know way it will fit . even though the piston is slightly smaller then the inner cylinder its not enough to be able to install a 1.5mm bigger piston.
Your piston has way too much play in it . it should not be that loose .
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Post by geh3333 on Jan 8, 2015 21:01:28 GMT -5
I have a 1P52QMI engine that i upgraded to a 150cc. Bought new head, cylinder, gaskets, and piston kit. Noticed over time It started loosing compression, even stopped sucking in gas from the floor tank. Wondering if the cylinder cutout is too big. I have a odd gap between the piston and the cylinder. (I only got the cylinder for $20 anyway). Changed the piston rings after 0 miles and still same problem. Oil pump works fine too. Is this normal? If so, how can I fix the compression? I also did the finger in spark plug thing and it didn't push my finger out. Wondering if I should have got the 149cm^3 cylinder instead... I set the valves to 0.05 intake and 0.06 exhaust i58.tinypic.com/11j7sc9.jpg JR, alleyoop, Doug, JerryScript, skuttadawg, So u bought the cylinder and the piston separate right ? If you buy a new piston ur gonna have to hone the cylinder , or you can buy the right cylinder for the piston u have and also buy a new set of rings . problem solved. |
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