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Discussion Starter · #1 ·
I have a smr 510 10’, fresh rebuild etc.
It will crank forever but not start. I’ve read about timing being 180 off, but i can’t seem to understand it. I did make the mistake of not checking if i was on the compression or exhaust stroke When installing cams.
Would 180 degree off mean i should take the cams and rotate them 180 degrees them mount up? But then i wont know if im hitting the right tooth on the freewheel because the circle on the cams would be at the opposite side? I’ll post some pics too. The first pic is the engine now. On tdc. I dont know if its the compression stroke or not, but i think it is. Second pic is the bile before, not on tdc for referance.

 

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Discussion Starter · #3 ·
New spark plug, new fuel pump, tried jumpercables so battery isnt the issue. I’ve checked everything i can think of.. the ignition timing being off is the only thing i can see as a possible culprit. I THINK the flywheel is positioned 180 degrees wrong in comparison to the cams position.. it seems like it fires the spark when the piston isn’t at the top. And yes timing on the top end is correct.
 

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Remember, the crank moves at 2x the speed of the cams. Your crank and flywheel don't know the difference between TDC on the compression stroke vs TDC on the exhaust stroke. TDC is TDC from their point of view.

If the crank is at TDC, and your timing marks line up, you're good to go.
 

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Discussion Starter · #5 ·
Remember, the crank moves at 2x the speed of the cams. Your crank and flywheel don't know the difference between TDC on the compression stroke vs TDC on the exhaust stroke. TDC is TDC from their point of view.

If the crank is at TDC, and your timing marks line up, you're good to go.
but there are no timing marks on the flywheel to worry about? Usually there is markings in the flywheel as well as the top, but no markingson the flywheel.. idk.. this is a head scratcher for sure.. Some people tell me something is 180 off andsome tell me that it’s good as long as it’s good on the top. The manual says to just put the piston Tdc and then time cams.
Some people tell me to buy a new throttle position sensor, but how do I check if there is anything wrong with the one I have?
 

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I'm not sure where the whole '180deg off' thing started, it was a BIG myth in the pitbike scene for example. As you noted, your manual says to put the piston at top dead center and then time the cams. Nothing about trying to figure out if the crank/flywheel are on compression vs exhaust stroke, etc. If your timing marks are correct when at TDC, I'd say timing is not a concern. Make sure the motor is at TDC when the marks on the cam chain sprocket/gear is vertical.

Now, your flywheel could be out of position on the crank, a sheered flywheel key is not unheard of, but pretty rare particularly if you haven't had it off. If you've got a flywheel puller, you can pull it to check. I'm assuming the bike was running ok prior to you getting into the cams, which would imply the flywheel hasn't moved.

Doing some quick digging, looks like you can't just meter out your TPS like I'm used to, meh. Again, if the bike was running before and you didn't monkey with the throttle body I wouldn't suspect the TPS to suddenly go south.

Go back to the basics, fuel, air, compression, spark and it should fire. Are you seeing a wet plug after trying to light it off? Have you verified you've got spark when you spin it over? Have you done a compression test?
 

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Discussion Starter · #7 ·
Thank you for a very detailed answer!
The thing is (should have mentioned it to begin with), That the whole engine is freshly rebuit (by myself i might add) whom has never been much of a mechanic. But carefully studying the manual and Yt videos got me through it. I also had the rest of the bike apart, and painted the frame.

so all in all, almost everything has been in bits. But it’s cranking normally, and everything is smooth. Just won’t catch on and actually fire up

I have checked grounds, spark, battery, timing, fuses, fuel etc. installed a new fuel pump, battery & spark plug just to be sure that it is all working.

there is one thing that I find odd about the bike now though. When I disassembled the throttle cables and throttle body, everything was working good and smooth. But now the throttle refuses to snap back. If I twist it, it is not rolling back 1mm. But if I disconnect the cables from the throttle body, and turn it by hand, it snaps back on the body.. idk if that has any relevance.
 

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Discussion Starter · #9 ·
The throttle issue screams cable routing to me, or the cables are adjusted too tightly, either can cause excess drag and prevent it from snapping closed.
Yeah okay, i’ll check the routing. But as long as the engine won’t start, fixing that issue will probably not help much hahah. I think it would be weird if for example the tps was bad, cause it was fine when I pulled it off. Bike was starting no problem.. so I believe there has to be something i have done in the process. Before rebuild it starts, after rebuild, no start. So essentially, it’s my mistake, somewhere.. mostly messed with the insides of the engine, and since it turns over nicely, all gears work fine and clutch is good, there must be something other than engine, like electrical or something.
I will pull off the flywheel Monday to check woodruff key. Maybe I should take off the throttle body as well to inspect for clogs or something.
 

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In these Husqvarna TPS, when it go bad, you cannot fix it, you need to replace whole throttle body(to me, when that TPS sensor is integrated in throttle body). I had bad TPS sensor, it was wild to handle, very bad starting, when you was getting engine running, you was need to all the time more throttle to keep it running. Not sure is work shop manual telling how to measure TPS without ibeat system or PC 5, when you can see TPS sensor readings from live at computer...
 

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Discussion Starter · #11 ·
In these Husqvarna TPS, when it go bad, you cannot fix it, you need to replace whole throttle body(to me, when that TPS sensor is integrated in throttle body). I had bad TPS sensor, it was wild to handle, very bad starting, when you was getting engine running, you was need to all the time more throttle to keep it running. Not sure is work shop manual telling how to measure TPS without ibeat system or PC 5, when you can see TPS sensor readings from live at computer...
where can I buy the ibeat cable? And is the software free? Only pay for the cable?
 

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