Hey guys, as the title suggests I believe I’ve a compression issue which is may be contributing to severe difficulty getting my bike to start. I’ve checked the usual things, spark looks ok, filter is clean and have tried starting both with and without it. Plug is wet after attempting to start and I also get pops and some backfire. Carb has been cleaned, jets seem clear. All jets are stock sizes. The only thing related to the carb I’m not certain on is setting the float height. Manual states 17.5-18.5 mm and arms should be parallel to the body but this isn’t possible to achieve if the height is to be correct. To get ~18mmi had to bend the arms about 5 degrees to get 18mm height. Allens Performance in the UK recommend the arms be parallel to the body but neither seems to work. I don’t believe timing is an issue as it has started a few times for me and runs fine once running. The battery has been replace as it was weak and had bulged. I performed a leak down test which according to my gauge was good (20-25%). There was no leakage on any valves as I had both header pipes removed as well as the carb and no hissing could be heard. So the I decided to to a compression test. It consistently reads 103psi which is down a bit on the target of 113psi. Would this reading be low enough to cause the non starting even though the leakdown seems ok? And if so that would mean new piston and rings I’d assume?
Engine rpm affects your compression test number,so i wouldnt mind it being little low. ESp with good leak test. Can you get it to run with starting fluid? New plug? not iridium,stock preferably. Husky manuals have several mistakes over years,so you cant blindly trust them. Jets are clean,are all passages too? incl air jets at backside of carb?( if there is any,in 05 there are.) Pickup coil ok? Strong spark?
Hey ceevu, I’ve been tinkering away on the bike without any succes since. I’ve tried squirting some carb cleaner and the like into the carb mouth and have gotten backfiring and flames through the carb. I’ve tried 2 new plugs which were a standard (CR7E). I’ve had the carb off a couple of times and I’ve checked all jets. Are the air jets on the filter side edge of the mouth? Not sure if I’ve checked those but I will. The pick-up coil was replace by me when I bought the bike as a non runner about 8 years ago as it was the culprit then. I’ve seen better sparks on other bikes but this has always been the same since I’ve owned it. Since i last posted I’ve gone ahead and replace piston and rings and the compression is up to 125psi. I was only intending to do the rings but they were impossible to get on their own. Piston is from a later model as the originals are discontinued. Still pops a little through the carb as before.
Did the piston/ rings solve it? I almost exclusively use leak down test over compression if cylinder health is the particular issue I'm checking. I'm unhappy and will be replacing parts with anything over 15% leakage, so I'd consider your 25-25% a failure (For reference, the last test I did on my '08 610 was reading ~6% after lapping the valves during a rebuild). I'd look into timing, valve clearances, and fuelling. Make sure the adjustments are within spec, and if you have aftermarket parts, I'd suggest deleting them one at a time to see if it fixes it (not permanently delete, just to diagnose). ps: where'd you get the piston kit from? and how much was it?
Piston and rings didn’t cure it unfortunately. I measured the rings and top ring was on the upper end of the spec, 2nd ring was ok but the oil ring was way out of spec so deffo needed replacing. Compression is now back up to 125-130psi. I rechecked the timing and it’s bang on. Valve clearance is 0.05mm as per the manual. I stripped the carb several times and all passages are clear, all stock jetting and stock exhaust. I had an aftermarket flywheel on it and also an original kuokosan denki flywheel and both were the same. I also checked the pick up coil gap and moved it closer to the flywheel which appeared to help as it miraculously started but wouldn’t start again after. Really annoying. Here’s a link to the piston for sale and a direct link to their website. I found them very good to deal with. https://www.ebay.ie/itm/26536908570...2JBMh7SRPu&var=&widget_ver=artemis&media=COPY https://www.fp-engineering.eu/
"Are the air jets on the filter side edge of the mouth" It seems you have some other carb(is it dellorto?) than newer versions does,so sorry to confuse... But In fcr,yes. Intake boot has no cracks?
The big 5: Air, fuel, spark, compression, and timing. You've seemingly eliminated compression and timing. Air is pretty straightforward (clean air filter). So you're left with fuel and spark. Have you tested the resistance on the ignition coil? Just because it's relatively new doesn't mean its good. I've had many come through the shop faulty straight from the factory. Hearing its not great spark and adjusting the gap helped makes me think that could at least be part of the problem. Have you tried manually priming it with a little bit of gas down the carb? NOT starting fluid or any other flammable spray. (one of those "squeeze/ mess free" style condiment bottles works well until the gas eventually degrades the rubber in the cap). Have you tested your fuel flow? Clean fuel filter? lines aren't plugged, pinched, or kinked? Was any work done to it before this? Or did it just start happening out of the blue?
Dellorto PHM40 carb on this model. Boot looks ok with no visible cracks externally that I can see. I have a second boot but I think it’s just as old.
The ignition coil needs to be checked. While I was putting the coolant hoses back on I said to myself I must check it but didn’t. As for the pick-up coil, I believe the expected resistance value to 100ohms and must check this also. Haven’t squirted fuel into the carb directly but have twisted the throttle a couple of times before attempting to start as it has a pumper carb. I’ve been using a remote tank while Troubleshooting and no blockages there. The bike was never one to start straight away, usually after turning over for a few seconds at least. It seems to have gotten worse over time until it refused to start at all.
Something that might be worth trying here. I just installed a NOCO NLP14 lithium ion battery and WOW that really woke her up when starting. The stock YXT14 batteries usually have around 200-280 cranking amps. This bad boy has 500! that plus the weight savings and less maintenance is an absolute win to me.
Havent been on here in quite a while so i thought I should give an update from a few months ago. My friend has an identical bike so I borrowed it to help troubleshooting. The first port of call was to swap the stator/pick up coil. BOOM! Started straight away! Damn pickup coil looks like the culprit yet again. @ceevu , you were spot on when you suggested the pickup coil @Shea , I would certainly consider one of those batteries if it gives my starting capabilities more oomph even though the price is a little saucy!
