Author Topic: Fl250 compression Problems  (Read 9387 times)

muzzfl250

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Fl250 compression Problems
« on: October 01, 2012, 12:48:39 AM »
New to this forum but in the process of restoring an 81 model fl250 and having some problems with TOO much compression!!  :o
with the plug out it turns over fine but is almost impossible to pull over with the plug in...any ideas/ help would be much appreciated!

hoodlum

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Re: Fl250 compression Problems
« Reply #1 on: October 01, 2012, 05:24:03 AM »
Is impossible to turn over or just hard?If it's just hard,get a compression tester,man up and jerk that rope a few times, and get a compression reading....If it's high,the head will need to come off....There are only a couple of things that will effect compression... Either the head is shaved, the head gasket is too thin,or carbon is built up on the top of the piston,in the combustion chamber,or both.......
Hoodlum

LiveWire

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Re: Fl250 compression Problems
« Reply #2 on: October 01, 2012, 01:40:01 PM »
The rope pulley in the FL250s pull starter is very small making it hard to pull over. It is common to see the bolt tabs of the pull starter crack and eventually break.

TEXASBAGMAN

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Re: Fl250 compression Problems
« Reply #3 on: October 01, 2012, 05:28:05 PM »
when you pull it with out the plug in it does alot of fuel/mix come out? crankcase isnt flooded? PLUG DRY? I know there is a compresion release but i never used one. search the forums info. theres always a GOKI starter!

muzzfl250

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Re: Fl250 compression Problems
« Reply #4 on: October 02, 2012, 01:18:36 AM »
top to bottom dead centre it moves fine but on the up-stroke, its almost impossible to pull up...ive had the head off and the piston has minimal carbon on it, i think its been changed recently but im not sure??? i brought it not running  :-\ i think the piston may be too large/cylinder on its last bore as it says 2.00 mm on the top...not sure?? and the pulley tabs were snapped when i brought it but recently fixed them.

TEXASBAGMAN

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Re: Fl250 compression Problems
« Reply #5 on: October 02, 2012, 05:10:27 PM »
I would remove complete engine from frame and take the cylinder and piston to engine machine shop. Let them measure cylinder bore and order or tell you what size piston to order. I have only used Wiesco Pistons but i think there are some other brands out there. Labor here is anywhere from $25-$50 to bore out a cylinder. New top end gasket set. Make sure there are no broken bits in the bottom of engine. If this is a repair you are planning on doing yourself i would be glad to help. Theres LOTS of folks here to help.

muzzfl250

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Re: Fl250 compression Problems
« Reply #6 on: October 02, 2012, 06:39:18 PM »
yeah, i was planning on doing that, the engine is already out...almost have it stripped back ready for a sandblast and powdercoat   :D
top end gasket looks alright but the bottom end definately needs replacing, ill get the calipers out this afternoon and give you some measurements of the inside diameter of the bore and O.D of the piston, you might be able to help!? cheers for the ideas anyway

TEXASBAGMAN

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Re: Fl250 compression Problems
« Reply #7 on: October 03, 2012, 09:09:16 AM »
service manual is the top of the fl250 forum. if its not i have it. section 8-14

TEXASBAGMAN

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« Last Edit: October 03, 2012, 05:47:44 PM by TEXASBAGMAN »

muzzfl250

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Re: Fl250 compression Problems
« Reply #9 on: October 03, 2012, 04:00:41 PM »
cheers for the site above^^ ill get some measurements and pictures and post them up to see if anyone out there knows whats wrong?
ill throw some up of the build progress aswell!!  :D

muzzfl250

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Re: Fl250 compression Problems
« Reply #10 on: October 04, 2012, 02:59:46 AM »
few shots of the head, cylinder and piston

hoodlum

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Re: Fl250 compression Problems
« Reply #11 on: October 04, 2012, 05:12:59 AM »
Ok....For one thing,your cylinder needs boring if there is room left...The walls are trashed....I bet the cylinder will need to be re-sleeved.....I also see either small pecks or pieces of metal laying on top of the piston....Either way,something in the lower end has come apart....I assume you never got a compression reading before taking it apart?
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muzzfl250

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Re: Fl250 compression Problems
« Reply #12 on: October 04, 2012, 06:01:53 AM »
the cylinder measured 71.8mm if that helps at all, with piston at 71.73...??? the marks in the cylinder picture arent indentations/scoring just a a bit of oil, what looks like bits of metal on top are actually tiny indentations i assume were caused by c=someone hitting with a centrepunch or something??? i think in the close past it has siezed... :-\ i attepmted a compression reading but my gauge wasnt working so ill have to get another...if in doubt, should i just get another head and cylinder??

hoodlum

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Re: Fl250 compression Problems
« Reply #13 on: October 04, 2012, 04:01:50 PM »
the cylinder measured 71.8mm if that helps at all, with piston at 71.73...??? the marks in the cylinder picture arent indentations/scoring just a a bit of oil, what looks like bits of metal on top are actually tiny indentations i assume were caused by c=someone hitting with a centrepunch or something??? i think in the close past it has siezed... :-\ i attepmted a compression reading but my gauge wasnt working so ill have to get another...if in doubt, should i just get another head and cylinder??

Last picture looks like a deep gouge above the exhaust port...I can actually see a notch missing in the upper edge of the port...Those little pecks are from something bouncing around in the combustion chamber...They are on the head as well....I would tear the engine down completely to see what exactly let go....

muzzfl250

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Re: Fl250 compression Problems
« Reply #14 on: October 04, 2012, 04:45:15 PM »
yeah, ill split the case as soon as i can get the the front clutch off...its well stuck  :-\ ill look again at the cylinder and get better photos, does sound like it needs a bore again...if itll handle one... :o