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Discussion Starter #1
Hey guys!

I have a Sherco HRD 125cc (probably no one ever heard of this) I bought it few years back and it had a Skyteam 125cc engine in it and the original engine came with the bike in box basically since the owner lowered the cylinder to get some more power i guess. The owner said that the engine only needed to be put back together and it would run and shouldnt have any problems...:frown: Well heres the story short, i drove with the bike some time until i got my driving license for car and it has ever since just stood unused(2-3 years now)
I have since started on assembling the original engine back together, but now i've ran into problem, i don't have right chain and sprockets for the bike so i cant roll it anywhere and i really want to see if the engine really does turn on, but here's the problem: I have the engine on the bike, i put fully charged battery into it, i click start button...nothing, okay it's bad solenoid/relay whatever you call it, i go ahead and short it out with screwdriver --> negative terminal starts to smoke and wires start to melt and the whole world laughs at me, then i take out the multimeter, i check the terminals on the solenoid and it reads 3-4v when just the battery is connected and nothing else is done, even the wire going to the starter is not connected to anything, when i connect the wire it reads straight up 12-13 volts on the terminal on the relay, does this mean its shortcircuiting somewhere? then i go ahead and disconnect the battery and put it straight to the starter...nothing, except few sparks and melting wire basically, starter says nothing even thought it just last year worked just fine connecting straight to battery, then i got ahead and find the Skyteam engine and connect the battery straight to that starter...it gives few sparks and thats it nothing else. Am i running with too weak battery for even the starter to think of turning? or whats going on, is it short circuiting somewhere ? or have my both starters suddenly gone bad? I really need some advice on this since i really want to ride it again someday, and i dont want to buy gears and chain for the engine if it doesnt even run. P.S. I know the solenoid is bad, it died long time ago when i was using the bike, luckily i had kickstart on it, this new/original engine doesnt have kickstart.
 

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Discussion Starter #2
P.P.S Its an old bike so no fancy electrical work in it,no computers just straight up old carburetor engine
 

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Okay guys, I dismantled the thing and what do you know, rusted and corroded. Now that i cleaned it, it works fine and dandy again.
 

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Another issue, might aswell put it here now that i've started this, i dont get the thing running, it doesn't seem to suck gas out of the carb, i have cleaned the whole carburetor just to make sure that isn't the cause. I tried squirting carburetor cleaner, i dont know if that helps at all with running. The carb is full of gas like it should be but its not getting anywhere seems like. So the question now is, does the engine need exhaust for pressure ? or should it start without the exhaust pipe on the cylinder ? and further most what could cause it to not suck gas, i did have a spark but again its a utility plug to say so, i don't know if its the right plug for the engine.What sort of test should i go thru here ? and i was wondering, i have a small ''tube'' coming out of the head of the cylinder and its blowing air out of that aswell, does anyone know what it could be ? its brass colored pipe about 3 cm long sticking straight up from the left side of the cylinder head
 

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That could be a vacuum line, but I'm not familiar with that motorcycle. You should always have the exhaust attached when the engine is running. The exhaust system does play a part in the mixture of fuel and air, with more open exhaust pulling more air and less fuel in the mix. I can't say if that is the only issue at this point.
 

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Discussion Starter #6 (Edited)
That could be a vacuum line, but I'm not familiar with that motorcycle. You should always have the exhaust attached when the engine is running. The exhaust system does play a part in the mixture of fuel and air, with more open exhaust pulling more air and less fuel in the mix. I can't say if that is the only issue at this point.
You mean the brass colored knob on the top of the cylinder head ? its rather large in my opinion the opening is about 1,5cm i guess it could be for temperature sensor now that i think about it, the funny thing is since the last engine didn't anything anything on the cylinder head, but it could be for oil temperature since its right above the where the timing chain is located.

EDIT: Someone tell me am i running the engine backwards or is it normal when i put my hand against the hole where the carb sucks air, its blowing out (?) and i noticed it was also squirting gas out of the hole on the carb, even thought it does blow air from the exhaust side aswell, its like, its pushing air out of every hole put not sucking in (?) do i have the timing backwards on it ?
 

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P.S uhhh so this is getting long thread but i hope someone will find the time read this all. It occurred to me that the camshaft gear where the timing chain goes to has 2 markings opposite of eachother, so could it be that the engine is 180 degree of regarding to valve timing ? since the internet really doesnt have any instructions regarding this engine (brand unknown) or the bike itself anyway, but since the principle is the same it should give you guys some ideas that i should try, so is the valve timing cause of air pumping out of carburetor ?
 

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The timing could be off 180 degrees if the timing chain wasn't put on the gear correctly. Make sure the piston is at top dead center with the cam gear and crank lined up with the TDC mark.
 

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Discussion Starter #9
The timing could be off 180 degrees if the timing chain wasn't put on the gear correctly. Make sure the piston is at top dead center with the cam gear and crank lined up with the TDC mark.
Yeah i have to take a look at it tomorrow, and it isn't 180 is it, if its upside down ? but me as a simple commoner learning all the time think it as 180 since its upside down, but yeah i will try that tomorrow and come back with the results. And the markings were all lined up, but the timing gear had those markings opposite side so it was like 50:50 chance that it will go upside down or not
 

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Yes, it's 180 degrees off on the crankshaft if the marks are lining up but it's on the exhaust stroke instead of the power stroke. The crank will spin twice for every one rotation of the camshaft.

To check, I usually turn the engine by hand until both valves open one after the other, then bring it up to the timing marks. You can visually check the piston is at the top at this time if you like as well.
 

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Discussion Starter #11
Yes, it's 180 degrees off on the crankshaft if the marks are lining up but it's on the exhaust stroke instead of the power stroke. The crank will spin twice for every one rotation of the camshaft.

To check, I usually turn the engine by hand until both valves open one after the other, then bring it up to the timing marks. You can visually check the piston is at the top at this time if you like as well.

Yeah so, i turned the wheel other way and still no luck, looks like ill have to dismantle it again and start looking for where i might have messed up or if my intake valve is stuck open
 

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Discussion Starter #12 (Edited)
Yeah so, i turned the wheel other way and still no luck, looks like ill have to dismantle it again and start looking for where i might have messed up or if my intake valve is stuck open

I did check how the valves move with the piston and i noticed that my intake valve opens little bit before tdc so that could cause the air blowing out of the intake port, right ? i did try to back the timing a little bit, but screwed it up totally and ended with piston hitting exhaust valve, need to try again tomorrow. But yeah could that intake opening too early cause this ? in my mind it could

P.S The timing marking on the flywheel is really rubbish, i only had that little piece on the flywheel basically marking tdc, the piece is like rectangle shape, which i guess would be the spark indicator since it was pointing up when the piston was at tdc. BTW how do i know which direction the engine is supposed to spin ? or does it matter ? the nut on the flywheel tightens clockwise, so in my mind it should spin clockwise so it doesnt come loose, but is there someway of telling this ? should i just power the starter and see which direction it goes ?
 

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Discussion Starter #13
I Got the timing on point now

I was wondering what could that black cylinder be and that small pipe on the valve cover if anyone know anything about something like this ?
 

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Discussion Starter #15
It runs !!! thank you for your help and suggestions!

The final issue was with the starter, after i had set the timing correctly.
The starter had rust in the coals and they didn't connect very well and the engine didn't spin fast enough to create enough compression/vacuum, but after cleaning the starter and trying again it fired after few spins.

Thank you all !
Ride safe !
 
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