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Engine bogs down under load it starts first kick and idles nicely and will free rev crisp. Riding up a hill with load it bogs down

It has me new top end, piston, ring, small end bearing and honed the barrel. I have put a brand new vhst26bs carby just like factory supplied and still has made no difference.

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Is the machine a two stroke? Because if it is a blocked exhaust (full of carbon deposits) will cause exactly this symptom. The best way to clean it is to stand it on its end and fill it with oven cleaner and leave it for a day. In the old days it was just a case of heating the exhaust with a blow lamp and tapping the pipe gently to loosen the deposits

Posted on Feb 03, 2015

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Check for a worn Crankshaft bearing and seal on the left side under the flywheel. Remove flywheel cover and try to move flywheel up and down by hand. If there is ANY moved or play then replace the BEARING and SEAL. If no movement then spray WD40 onto crankshaft seal while running and if bike speeds up replace seal. Good luck!

Posted on Mar 21, 2014

  • mark hughes
    mark hughes Oct 10, 2014

    Check, plug gap .


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Posted on Jan 02, 2017

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SOURCE: Engine cut out under revs but will idle

fueling problem. its not getting enought fuel from the carb. check the pipes, jets and floats.

Posted on Jan 14, 2009

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SOURCE: i cant get my 2003 kx 125 to run properly

Remove the slide from the throat of the carb, move the clip on the jet needle one notch lower. This will richen the low end fuel/air mix. - - - Simple, quick, and free.

Do it, then rate this answer as "Very Helpful". Thanks.

Posted on Jun 19, 2009

  • 375 Answers


Who jetted it? Sounds like an air leak. Check your manifold.

Posted on Jun 29, 2009

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SOURCE: Yamaha 2001 ttr 250. Bogs above half speed, under load

I have the same problems with my 1999 TTR 250, were you able to find out anything?


Posted on Aug 07, 2010

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SOURCE: pw 50,

cover up the drilled holes this can cause problems, why was a new carb fitted? did the shop have it running?
not likely rings .
check carb for flooding and correct jet sizes.
check safety kill\start\run switch for shorts.

Posted on Feb 25, 2011

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02 ford 4.2 f150 blue smoke a lot just rebuil motor

did you hone the bores before fitting new rings ( old glazed bores will not allow new rings to seal properly)
did you space the ring gaps around the piston and not have them all line up ( if the ring gaps were not spaced around the piston , the oil will pass straight up the gap and be burnt in the combustion chamber --alternately the flame of combustion will get to the sump down the gap)
did you take care as to which way up you put the rings on the pistons ( there is a top etched on each ring and if this was not adhered to then the ring edge acts as a scraper and pumps the oil into the combustion chamber . also the compression pressure cannot get behind the ring to force it onto the bore wall
did you fit new bearings to the big ends ( old bearings will allow more oil onto the bore walls and this makes controlling the oil by the oil ring difficult)
did you fit the valve stem seals correctly( if they haven't been fitted correctly then the vacuum from the idling will suck oil past the valve stems
If you missed one or more in the rebuild then that is why you are burning oil

Nov 05, 2015 | Ford Cars & Trucks

1 Answer

How do I install new piston in a homelite XL2 auto chain saw

up from the bottom of the cylinder
make sure that the ends of the ring is at the locating pin in the ring groove
pull the conrod right up and put a set of vice grips on to hold it up position the barrel over the piston and hold the ring in with your fingers
gentle push the barrel over the piston and the taper at the cylinder base will hold the ring in as you continue to push the barrel down
if you have failed to correctly align the barrel on assembly then make sure that the piston is at the top of the stroke before turning the barrel around as the ring ends may catch in the ports of the bore and break the ring.

May 30, 2015 | Homelite Garden

1 Answer

Just put in s new top end a yz 85 2008 , wouldnt start but could if it was bump started and ran bad. Opened her up again and there was marks all over the piston, help??

When fitting a new top end you may have broken the piston rings. On a Two Stroke engine the rings have a gap which must not enter any ports. To prevent this the slot for the rings has a metal peg to hold the ring gap in one place.
On Four Stroke engines there is no ring peg as there are no ports.
If a ring breaks whilst being fitted the broken parts will enter a port and then be dragged up and down the barrel causing damage to piston and barrel. The broken parts one having made their way to the top of the piston will be crushed between the cylinder head and the piston damaging both. The cyl head can be re used but the piston is most likely ruined.


Oct 03, 2013 | Motorcycles

2 Answers

Hi,redone the top end of my Rm125 1989,it struggled to reach powerband for a while, but eventualy it reached it!Next morning I started the old lady and there was almost no compression with a funny noise in...

Hi, i presume that before you rebuilt the top end you had no issues? Normaly this happens when either you have exsessive play in either the big end or the small end bearing, this would be recognised by up and down moovment in the conrod for big end and piston for small end, this would account for spark plug contact only. The other thing to check was the piston identical in height to the old one, did it have the same cut outs for fuel transfere, and finaly did you install it in the correct direction with the rings located in the peg positions facing the inlet side of the barrel, was the new head gasket the same thickness as the old one, did you run i the new piston for a while if the piston and cylinder were new a bed in period must be observed

Mar 13, 2011 | 2003 Suzuki RM 125

1 Answer

Their is a Ta pit sound,yes the oil is burning,no,i had a problem with the bore,when local mechanic opened the bore,he showed that the rod is shaking,it has to be replaced,to replace he has to open the...

Yes. He will need to split the case to get the conrod out. Here's what you can expect to change, probably the piston and barrel. If the piston does not have lines on it and the rings still fit tightly in the grooves, you might be able to do a rings job and hone the barrel. You will need to replace the gudgeon pin bearing and big end bearing. If the crankshaft has marks on it that will need to be replaced as well. He should also replace the crankshaft seals. You might as well put in a new oil pump and have the valves re faced. At the end, if your mechanic is good you should have a good engine. You might find it cheaper to find a similar bike with low mileage that has been in an accident. It will be a lot easier and cheaper to take out your engine and put another one in. It would take a couple of hours.

Mar 02, 2010 | 2005 Bajaj Pulsar 150

1 Answer

I have a honda 100cc lead scooter+it seems to be running rich,+ using alot of fuel,how do i cure this

Go straight to the carby turn the mixture screw all the way in then back it out 1&1/2 turns if this fails to cure the running rich & excessive fuel consumption then you need to be looking at doing a compression test if the compression proves to be low you will need to over haul the top end it may be that a light honeing of the cylinder & a new set of rings will remedy the problem worst case scenario rebore new piston & rings valve guides reseat valves.

Feb 22, 2010 | 2005 Honda Spacy 100

1 Answer

What is a top end kit for a suzuki ay50 and how easy is it to fit

a top end kit consits of a 1x piston 2x circlips 1x gudgeon pin 1x set of rings and 1x gasket set basically you take the carb off take the exhaust off take spark plug cap off undo bolts on head/barrel remove gasket slide the barrel off removing bottom gasket then take the circlips off 1 side then push the pin through i put a piecwe of card bord or rag in the crank to stop **** falling down through when you slide the pin out the piston will come out then you will see a bearing in the con rod leave that in there then get new piston put ciclips in one side then get the gudgeon pin put some oil on it and put it in place of the little bearing the push the pin through and put the circlip in and then put the rings on then in the ring gap you will see a little pin the gap in the ring goes in beetween that little gap then you put the base gasket on then inspect the barrel if there is dips in the lining re hone it or get some glass paper and rub it till its smooth but not too much or it will rub down to much then rub some oil in the barrel then put the barrel over the piston and compress the rings and slot the barrel down the pistonand put head gasket on and put head on and tighten bolts/nuts then replace carb good luck

Aug 22, 2009 | 2001 Suzuki AX 100

1 Answer

Using oil after 1/2 top end rebuilt what type oil do u rec.

re- strip top end, hone cylinder bore and then re-assemble piston, rings and cylinder dry, yes that's correct use no oil on piston assy. apart from gudgeon pin. Has the valve stem seals been replaced?

Apr 13, 2009 | 2002 Honda XR 200

2 Answers


excessive piston clearance.really needed bore job with oversized piston,not just honed and rings.measure piston to cylinder clearance,check spcifications and verify

Apr 05, 2009 | 2003 Yamaha YZ 125

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