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Old 21-12-17, 10:42 PM   #11
machulnyy
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Default Re: Curvy Cold Starting Needs Running Start

Hey guys. Been a while...I came off on that weekend before I had the chance to try everything! Sad times as am still waiting for the shifter to arrive from America..

But here is the interesting part...

Before I came off, I had the chance to check the airbox (thought would start with the easy stuff before getting to electrics). And after removing it I find petrol (edit: could have been oil...forgotten by now!!) inside. This could explain the choke issue right? But how could it have gotten in there??! So i cleaned out the liquid from the airbox and run a bit of fuel system cleaner through it and rode out to my friendís. The next morning it had trouble starting again but did eventually, I rode for 5 mins and came off. Took it back to his where it is now. Came back a week later to have a look at it and it started first time without problems! I think this is because the connection in the starter motor jolted back into place or something?? But now the exhaust sounds different...more muted and not as crisp and raspy as before and backfires every now and then on idle. Yet another mystery to solve.

To sum up: I think Biggles is right in that there were/are two problems: starter motor and choke.

The choke issue seems to be something to do with the presence of petrol/oil in the airbox (is this what running rich means?). Ordered a new filter. But how did it get there? Whatís the cause?

The starter motor issue (as my car mechanic friend explained) could be something to do with worn out brushes which causes motor to short (im paraphrasing but he seemed to be sure of it as soon as I described the symptoms). The fall may have shifter the position of the brushes which is why it now starts well again. But have Ordered the back part of the starter motor to replace.

If these fail, will get to examining the electrics.

But now, the issue of the backfiring...does anyone have any ideas?
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Old 22-12-17, 11:02 AM   #12
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Default Re: Curvy Cold Starting Needs Running Start

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a little oil in the air box is not unusual often caused by wear on the rings/bore, it gets there by the engine breather. The worn rings cause the crankcase to pressurise and the crankcase breather, which alleviates the pressure, is fed into the airbox.

Backfire? either the mixture is wrong or the plug isn't firing every time and when it does fire it ignites the unburnt fuel in the exhaust. Were you running it without the airfilter (this would cause a weak mixture). How old are the plugs - what do they look like: wet or sooty or light brownish-white (should be the latter).
Can the rings be changed? Where do I find them?

The plugs were changed not a week before the crash. Brand spanking new.

No I put the old filter back in prior to riding it.


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Old 24-12-17, 10:21 PM   #13
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Default Re: Curvy Cold Starting Needs Running Start

Hmm my money on the backfiring - which I'm guessing is more of a pop than a gunshot - is a stuck choke and it's all running rich. Nothing to do with oil in the airbox - mine gets this now and again if I cane it, it builds up slowly really. You need to check the cable for kinks and make sure it has enough slack in it. Also check where it splits as this little box is easy to break. You could do with getting the plungers out and checking for rust etc. build-up on the seats. If you follow the cables to the two carbs, you need to undo the single screw of the retaining plate, and carefully pull out the plunger - if in doubt, pull the choke lever right back first and nothing will fall off. Check the recess for crud, repeat for the other carb. The screws and be stuck fast so use a good-fitting screwdriver and try not to chew them.
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Old 28-04-18, 03:44 PM   #14
machulnyy
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Default Curvy Cold Starting Needs Running Start

Hey guys. Been a while. A lot has happened since...

After a difficult time starting on a particularly cold morning, got it going but noticed the gargling backfire was worse than usual. Cranked up the choke. After a few hundred metres, pulling up to a traffic light, noticed the revs dropping and the gargling g continued. Upped the choke. On the dual carriage, plodding at about 70 to warm it up. Traffic ahead, rolling off the throttle and when at about 2-3k revs, it shuts down completely. Would not start up again while still coasting. So I coast off the side off the curb (lucky was by a stretch of curb with a parallel road rather than just a wall). Trying to start with no such luck. This time not even a hiss, click, fizz, bang, crackle or pop...nada. Other electrics showing signs of life though with the lights, hi beams, indicators, horn as well I think. Just no ignition. Left it there and took the bus to work. Friend picked it up with his van in the eve. By the tine get to mine, van stank of petrol. Could see petrol on the right side of the engine, looks line came form front carb.

Figured it was a blocked carb so I stripped them off the bike and cleaned them myself, getting all the jets, float needle and seats etc...the whole shebang. Also, as someone had suggested, took off the starter motor and replaced the brushes. When the weather picked up, got to work...connected the carbs back up, checked and lubed the throttle and choke cables as you guys suggested, inspected the electrics as much as was easily accessible, reinstated the starter motor, charged the battery. Started right away. But then it didnít, so replaced the starter solenoid, same story. Then done what I should have checked first, the clutch starter switch, cleaned it and that seemed to have done the trick. Started perfectly and ran flawlessly...no leaks. Gave it a thorough clean, cleaned and lubed the chain, changed the oil. Next day was ecstatic to be riding to work again.

In the morning had a tiny hitch when starting but nothing major and started pretty much right away. Got to work. 8 hours later thought, the difficult starting began again. A minute of struggling, got it going. Next morning much worse. Took 5 minutes to get it turning over (see vids at below link). Basically same problem began. Oh and some petrol and oil comes out of then left side hole in the engine (rear plug drain hole??) when starting only. Got worse after work. The following night I decided to take off the battery to charge it in case the problem was with the rectifier (nope. Battery was fully charged). There was a strong smell of petrol and having a look (the first two vids at the link) I could see the petrol stains on the left side of the engine and some deeper inside.

So basically am now even more lost than ever. The difficulty starting seems to be inherently linked to the petrol leak. But why it started leaking again is beyond me. Only took two trips for it to come back. What could it be??

https://www.icloud.com/sharedalbum/#B0BJ0DiRHGNU4RA (the videos are in reverse chronological order)





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Last edited by machulnyy; 28-04-18 at 03:50 PM.
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Old 29-04-18, 02:05 PM   #15
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Default Re: Curvy Cold Starting Needs Running Start

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Firstly, I admire your patience, these faults can drive you crazy.

Petrol leak: might be a sticking float valve. I'm never sure how much to say in case you're familiar with how it all works. The bottom of the carb is basically a little petrol reservoir known as the float bowl, petrol is pumped into the bowl until the float which is located within the bowl rises to a set level at which point it shuts off a small valve. These valves can stick which would cause a problem (with leaking fuel) if the engine was running. The curvy has a mechanical fuel pump that requires engine pulses to operate a rubber membrane which pumps the petrol. I don't know whether the pump can leak - IF it can leak and IF the float valve stuck, the float bowl would overflow (but usually down a drain tube under the bike). Whatever, it sounds like the tank and carbs need to come off again. You can get inexpensive carb rebuild kits off ebay which contain new float valves - you can check the valves by blowing into the carb (where the petrol would normally go) and gently raise the float to see if the airflow shuts off. Incidentally, the float level is critical so be gentle with the floats - adjustment of the float level is usually done by bending a tab on the float itself (height spec in manual).
The curvy manual shows how to test the fuel pump and the fuel valve. There are a lot of rubber membranes in the fuel system which may be perished which are causing your problems.

The video that shows you unsuccessfully trying to start the bike - it sounded to me that it was cranking slowly because of a flat battery.


You have no idea. Was verging on tears when the leak returned .

Right. So Iíve ordered a rebuild kit for each carb. Once they arrive, will take the carbs off and rebuild. Will then test the integrity by blowing into and adjusting the float to see if it shuts off the airflow. (Will check the height of the tab in the manual)

Will then look for how to test the fuel pump and valve in the manual.

Will report back once have tried, unless anyone has any other ideas I could try while the carbs will be off?? Appreciate all your help.



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Old 30-04-18, 05:30 PM   #16
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Default Re: Curvy Cold Starting Needs Running Start

whats rining my alarm bells is:
1. sidestand switch or clutch switch is fubar. when these go you can usually start the bike when the sidestand is up or down depending on what mode the switch is stuck at. problem is the SV has a "check" built into the ECU so a fubar switch will stop the bike from starting. sometimes giving the bike a push start will "jiggle" the switch enough to let the bike start.

2. smoke from the drain hole, thats mousture so water is getting into the plugs. if water is getting into the plugs it will trap itself under the plug cap causing arching and eventually break down the plug insulation.
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Old 10-05-18, 09:45 AM   #17
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Default Re: Curvy Cold Starting Needs Running Start

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on the 4th video, the one that lasts 11 seconds showing the rear cylinder plug drain hole - is the smoke coming out under pressure? I cannot decide whether it is or not, wouldn't the smoke have risen up near the spark plug itself rather than coming out of that hole? Is the spark plug secure and seated properly or did you video it on a windy day?

Have you cleaned out the drain holes?


Not really under pressure, just kind of seeps out. Wasnít a windy day. Havenít cleaned out yet...didnít know I could/ should. Will do this eve along with checking the seating of the spark pluga!


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Old 10-05-18, 09:46 AM   #18
machulnyy
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Default Re: Curvy Cold Starting Needs Running Start

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Originally Posted by Seeker View Post
on the 4th video, the one that lasts 11 seconds showing the rear cylinder plug drain hole - is the smoke coming out under pressure? I cannot decide whether it is or not, wouldn't the smoke have risen up near the spark plug itself rather than coming out of that hole? Is the spark plug secure and seated properly or did you video it on a windy day?

Have you cleaned out the drain holes?


Not really under pressure, just kind of seeps out. Wasnít a windy day. Havenít cleaned out yet...didnít know I could/ should. Will do this eve along with checking the seating of the spark plugs!


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Old 10-05-18, 09:52 AM   #19
machulnyy
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Default Re: Curvy Cold Starting Needs Running Start

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there's a tip here on post #14 for one check for the petcock (the vacuum operated valve that allows petrol to flow when the engine is running):

http://www.svrider.com/forum/showthr...=117517&page=2

If the petcock and/or fuel pump is or has been leaking you may want to do an oil change in case any petrol has got into the oil.

If you do a search for SV650 carb leak, you'll find that stuck float needles, leaking petcock and cracked fuel lines are common problems on curvys. You might want to look up hydrolock too (bearing in mind that I'm always pessimistic).


Ahh this so sounds like the problem! Just went down to smell the oil gasket and it smells of petrol! Hydrolocked

Now to find the cause of the leak, right? First will check the fuel pump/ petcock. Then the carbs...have received the restore kits last week


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Old 10-05-18, 09:57 AM   #20
machulnyy
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Default Curvy Cold Starting Needs Running Start

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Originally Posted by Bibio View Post
whats rining my alarm bells is:
1. sidestand switch or clutch switch is fubar. when these go you can usually start the bike when the sidestand is up or down depending on what mode the switch is stuck at. problem is the SV has a "check" built into the ECU so a fubar switch will stop the bike from starting. sometimes giving the bike a push start will "jiggle" the switch enough to let the bike start.

2. smoke from the drain hole, thats mousture so water is getting into the plugs. if water is getting into the plugs it will trap itself under the plug cap causing arching and eventually break down the plug insulation.


Hmm...good shout. the switches could be a culprit also as I did initially think it could have been the clutch switch..didnít think of the stand one. Is there any way of telling without replacing?...will check these once Iíve run through the hydrolock symptom checklist. The petrol smell from the oil gasket is a strong indicator that that is the problem though I reckon


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Last edited by machulnyy; 10-05-18 at 09:58 AM.
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