pete_b Posted July 9, 2011 Share Posted July 9, 2011 Rings Fit with the ends each side of the little nipples so they cannot turn around. Can you find out what the squish measurement is? This is the gap between the top of the piston and the head when the piston is at top dead centre. To measure it get a piece of solder bend at 90 degrees (with about 25cc bent out) remove the plug put the solder down in to the hole so as the 25mm bit is parallel to the piston top and turn the engine over slowly (you may have to bump it up and down by holding the fly wheel, this will flatten the solder when the piston goes over top dead centre. Carefully pull the solder out and measure where it has been squashed flat, this is the squish measurement. If the measurement on yours is to small (high compression) then add a base gasket or how ever many it needs to get the measurement correct. This will bring the compression back to standard, or you could just use a compression tester (but this would need the engine turned over a few times in one pull. Quote Link to comment Share on other sites More sharing options...
helimed01 Posted July 13, 2011 Share Posted July 13, 2011 Hi. The Walbro carb needs vacume from crank to suck fuel. It receives this from one of 2 ways. From the crank via an extra rubber tube to the non diaphram side of the carb: Or from a tiny hole in the carb that matches up with a hole in the barrell however this hole is often blocked by the gasket or extra sealant people put on. Most manufacturers including H&E fit an extra rubber pipe from the crank to the non diaphram side of the carb to provide vacume. If you purchase a new carb the backing plate will be missing this nipple that connects the rubber tube, therefore you are not supplying your motor with fuel hence difficult to pull. When I bought a new carb I had to use the old backing plate with the nipple bit on. Just an idea. hope it helps. regards. Quote Link to comment Share on other sites More sharing options...
pauldeakin Posted August 3, 2011 Share Posted August 3, 2011 Before you start looking at ignition timing -Is your drive belt loose? does it squeek? If it is loose it will not act as a flywheel to get you past the compression when you pull start. Try over tightening it a little and see if it pulls over easier, it does then set it to the correct tension, if it slips when set to the correct tension, try a drive belt dressing that makes it stick better. Paul D Quote Link to comment Share on other sites More sharing options...
clivefreeman Posted August 3, 2011 Share Posted August 3, 2011 I think its a clutched h&E Quote Link to comment Share on other sites More sharing options...
geckofly Posted February 25, 2013 Share Posted February 25, 2013 Hi Guysi reported some time back that I was having some issue with a friends HE 120 paramotor I was having the same issue as Clive with there being way too much compression. I have reported the issue to HE paramotor in Spain and they have being great but I am in Australia there are in Spain so its all emails to and from. So way too much compression to the stage it is near impossible to pull start. Remove spark plug all good. So far I have followed the step from the link in the second post in this link: viewtopic.php?f=4&t=6214 I recevied a new gasket which was meant to resolve the compression issue (which it has not) and some new O ring for the cylinder head. I have cleaned the Piston and the cylinder following the guide by Alex Varv http://www.aerocorsair.com/id107.htm I have now put it all back together and I still have the same issue, there is no decompression hole I have looked everywhere!! I am at a loss now, I am now thinking its a carbie issue as it there is no fuel reaching the shiny piston head not a even a hint of fuel. Anyone out there have any ideas of where the possible issue is, Its driving me nuts plenty of head scratching. If I remove the carbie will there be a whole world of pain trying to get it back in good running order. Any ideas would be greatly appreciated. Dara Hi Dara Im having the same problem with a PA125. although it does have a clean decompression hole ! .was it the timing?did you ever get to the bottom of this? Quote Link to comment Share on other sites More sharing options...
tortoise332 Posted February 25, 2013 Share Posted February 25, 2013 Use to have the same problem on a generator i have every now and then it would do this it had me for a while then i just kept pressure on pulled cord For 10 to 20 seconds if its a direct drive no clutch turn the prop make sure you turn motor off and take html lead off your only trying to turn motor over not start for now should be able to here the air getting sqeased past the piston Cheers Gary Quote Link to comment Share on other sites More sharing options...
geckofly Posted February 25, 2013 Share Posted February 25, 2013 In Case anyone else has come across this problem and it is found not to be the timing . I talked to Pierre from PAP he suggested two things the Gap between the coil and flywheel should be 0.6 not as it says in the pdf 0.4 Also suggests it could be wear on the starter mechanism , which locks up when a lot of tension is applied. mine certainly shows alot of lateral movement! and its interesting that this was noticed in previous post I have now noticed that the pull start mechanism is now looking a little worse for ware from all the excessive pull due to the hard compression. and it sort of maybe ties in with the generator fix thanks for the ideas will try tommorrow! Quote Link to comment Share on other sites More sharing options...
notch Posted February 26, 2013 Share Posted February 26, 2013 My starter also has a lot of lateral movement (100+ hours). But it seems to start okay. My PA125 does have more compression than any of my friends motors though, and is harder to pull over. I know of one expert on these motors that enlarged the decompression hole in the cylinder to fix this issue, with no resulting loss in power. But it's a one-way operation, and you have to be careful with the plating on the cylinder walls. Another option is to try a larger thickness base gasket. This increases the volume at the top of the piston stroke, reducing compression. I have had to do this as the quality of fuels in the country I have moved to is very poor, and detonation occurs without this change. Thanks for the update to the 0.6mm gap on the flywheel... Quote Link to comment Share on other sites More sharing options...
geckofly Posted February 26, 2013 Share Posted February 26, 2013 My starter also has a lot of lateral movement (100+ hours). But it seems to start okay. My PA125 does have more compression than any of my friends motors though, and is harder to pull over.I know of one expert on these motors that enlarged the decompression hole in the cylinder to fix this issue, with no resulting loss in power. But it's a one-way operation, and you have to be careful with the plating on the cylinder walls. Another option is to try a larger thickness base gasket. This increases the volume at the top of the piston stroke, reducing compression. I have had to do this as the quality of fuels in the country I have moved to is very poor, and detonation occurs without this change. Thanks for the update to the 0.6mm gap on the flywheel... Thanks for the info Notch I did change the base gasket. I made another out of 0.6 paper and with a bit of gasket sealer put it on top of the other one now the squish is slightly over recommend 1.5 /1-6 but will probably bed down a bit , But at last it works!!! also reset the magneto gap it was a little off but not that bad Put a sleeve and brass washer in starter this reduced the play (but not sure this had much effect) anyway something did the trick! forgotten how sweet it all sounds Really didnt fancy drilling out cylinder ! Quote Link to comment Share on other sites More sharing options...
simonmarshall Posted August 9, 2013 Share Posted August 9, 2013 I had a similar issue on a PAP ROS 125; I serviced the carb, changed the spark plug, replaced the coil, checked the timing until I found the problem. The compression hole (small hole inside the cylinder just above the exhaust outlet was cloggeed up, causing very very hard compression (amazing it can make such a big difference). Simon Quote Link to comment Share on other sites More sharing options...
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