80 psi is far too low - it should be at least 140. And 10mm (if that's the valve clearance) is ridiculous.......

 

My bad. I ment 0.10mm. How else can I give it more psi. The barrel and piston and in good condition. And all new gaskets.

Just checked the manuAl. It says 92psi

 

Don't forget that the automatic decompressor reduces the effective compression when cranking over. You're not too far off at 80psi.
If the bike has been standing it will be a Sh*t to get it going.
Make sure you're using fresh fuel, drain the float bowl and refill if in doubt.
Remove the airbox to carb snorkel and put your hand over the carb mouth to increase the suction.
Is there a good spark?

 

Hi. Thanks for a reply. I have removed the carb and cleaned it out about 3 times. It has a good spark. And new plug. Fresh petrol.. fully charged the battery. Used easy start (alcohol so helps the engine fire) still nothing.

The bike was stood up for about 8-10 months in dry storage. All electrics work. So I'm not thinking it's the cdi/ecu.

Honestly I have worked on it. It just p*sses me off every time I work on it. As it only needs a few hundred rpm to carry on.

I was thinking of advancing the timing. And seeing if that would help but not sure.

And I'm completely out of ideas of why it's not running.

Thanks for the reply.

If you think of anything else please reply. I was very close of pushing it off a cliff. But it's too heavy to push up hills...

Many thanks Owen

 

I dont think you can change the timing TBH, where are ya in Devon ?

 

Hi. I'm in Torquay.

I thought u could advance it by rotating the flywheel

 

Unlikely to be timing....
If you have good spark unlikely to be side-stand switch etc.
Is the plug getting wet with petrol when you try starting?

 

Second piston and barrel sounds like a recipe for a shit engine.

Theae motors will run with surprising low comorss though, although not well.

Ia everything else on the bike standard ??



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Hi. When I got this bike the barrel and piston where shot. I mean. The piston exploded. So stripped the engine and removed all the piston. So bought a slr650 barrel and piston from a working bike.

The head is OK. And so are the valves.. complete new gaskets as well.

 

Hi. The plug is dry but black with carbon.also it's a new plug. Have tried pouring petrol into the venturi and no improvment took the plug out and put a little petrol into the bore put plug back in. And still no improvement....

 

I would like to heard about wet but clean spark plug.
You could have a duff new plug - try a cleaned old one.
Are 100% certain cam timing is correct?

 

Hi. The timing is done right. I followed the manual. (Also I have been to college for motorcycle repairs) but this bike is just a pain.

 

If there's no fuel getting through then surely that needs further investigation - is it gravity fed from the tank or vacuum operated fuel tap?

Though odd that that even with easy start there's not a hint of it catching.

 

i think its gravity fed, (I think)
the bike fires and smoke out the exhausts, but it wont carry on, it gets to about 900RPM and it needs a few 100 RPM to carry on. when its running at 900ish RPM i then put a little bit of easy start, it just dies. I know this is over fueling it, but will a small amount of easy start shouldn't kill an engine and make it stop (fuel mixture is set to standard)

Many Thanks Wychwoods

 

A small amount of easy start will kill an engine off idle. Its for starting, nothing else. It can work with your throttle wide open but ive rebuilt and fixed countless of these motors and easy start has NEVER worked.

If your bike will run on idle but die on anything past idle then it can only be a few things.

Either your carb isnt fueling enough (perhaps blocked float valve or blocked main jet). Sounds like its only running on the pilot circuit to me. Loosen the carb drain screw. Do you get a constant stream of fuel with the fuel tap turned on ?

These motors, like all motors have a timing advance. On these specific engines, its called a timing 'boss' and its what the pulse generator picks up on

When the timing boss or CDI has been changed and is incompatible, your ignition wont advance past idle (common problem when people put SLR, FMX motors in dommies and vice versa).

Your coil is bad (Buy a new genric two-pin on ebay for £10)

This is all assuming your valve timing snd second hand engine parts are okay. However, If the bike will idle then it should also rev-up

Good luck

 

Hi. I can't get it to idle. It's just under idle.

I will try and clean the carb out again and go in with a toothbrush and clean it 100% not just a general clean...

The bike was running before the piston exploded. And I asume all electrical parts are the same and not changed.

The coil replacement might be a good idea.

I will try to make a video and upload so you guys can see what's going on.....

Many thanks Owen

 

Apart from the good idea about new Coil, it does sound carb related.
Are you certain neither of the carb diaphragms are split or damaged and vacuum circuit not blocked or perished.
I would set Idle Mixture to 2.5 out not standard

 

Hi. Yes both diaphragms are fine. Not stretched or ripped. And the vac is fine no holes etc etc.

 

Remove and earth the plug against an unpainted part of the motor and turn it over. You need a constant, fast bright spark.

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His. The plug is sparking well with a VERY bright spark and a nice cracking sound when it sparks..

 

when you reassembled your head did you make sure the decompression plunger and spring were refitted ? engine wont run without it,
or maybe with all that schrapnel floating about a piece could have wedged the plunger in position

 

hi, i have put the little "pin" with the spring back in. and still nothing. i will have a go tomorrow, i was looking through the manual, i was thinking it might be the throttle position censor, or spark coil....

i think it might also be the cam chain sprocket on the crank, i think it could be a tooth or two out, making it spark before its needed, (after TDC not before) this would also make the PSI increase...

 

The timing sensor on the crank will only go on, one way.. you cant adjust it or get it wrong unless you change it for one off a Dommie etc.

The spring plunger will stop the bike running too. It needs to move freely and not stick.

Are you sure you set the crank to the 'T' mark on the alternaror when setting your cam timing ?

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can you confirm that when your timing marks are on T that the piston is actually at tdc ?
years ago when i was rebuilding a basketcase xr250 i discovered that the woodruff key had sheared and the flywheel had rotated on the crank and wedged in position way out from where it should have been,
i didnt work this out until after i had refitted the head and tried to start it,
wasnt until i whipped the head off again and turned the piston to tdc and the flywheel was nowhere near that i understood why it didnt want to start

 

hi, yes i have put it to T on the fly wheel and the sprocket on the cam in the head is set right, two marks level with the casing, and out on the side of the exhaust,

i might look into TDC on flywheel but not a true TDC,

i started work on this is morning, it started to rain (i have to work outside) and tbh it doesnt look like it will stop....

 

think you misunderstand what i was saying,
on my xr i set the flywheel on T but it wasn't actually tdc because the flywheel had rotated on the crank,
so after getting the cam set in position with the T mark it was actually nowhere near tdc,
quite probably your problem lies elsewhere its just another possibility to cross off the list