Slight misfire after 10 year layup

[netsurfer]

Got a secondhand set of carbs on my SV650s-K1 as the originals were in a bad state after 10 years lying up. New set of plugs and it started up pretty easy, water circulating & thermostat opening.

No bad sounds other than this slight misfire at idle. Any suggestions? Youtube Link

Next step is to fill with fresh coolant and oil/filter when I can confirm I dont need to remove any more bits

Cheers
Pete

[Seeker]

Many years ago I had an awful piece of German engineering; a VW Polo. I took it to be Krypton tuned (remember those?) and the mechanic said: "Are you sure you want me to do it with a burnt inlet valve?" It sounded a bit like your SV.
I suppose an air leak might cause it - if you spray the intake rubbers with WD40 the idle will stumble if there's a leak. Where are your air screws set to? (2.5 turns out is normal). What happens above idle revs, what does it ride like? Have you checked compression? Valve clearances? I suppose the big question is why was it laid up 10 years ago?

[R1ffR4ff]

Originally Posted by netsurfer

Got a secondhand set of carbs on my SV650s-K1 as the originals were in a bad state after 10 years lying up. New set of plugs and it started up pretty easy, water circulating & thermostat opening.

No bad sounds other than this slight misfire at idle. Any suggestions? Youtube Link

Next step is to fill with fresh coolant and oil/filter when I can confirm I dont need to remove any more bits

Cheers
Pete

Is the fuel fresh?Also I'd slam a half a bottle of Redex or similar in the Tank and give the bike a good blast but also do as Seeker says and check for air-leaks around the Carb intakes and check for exhaust leaks.Also if possible check the choke plungers but use the correct JIS Screwdriver on the screws if possible and plenty of release fluid as they are easy to damage.

[netsurfer]

Will check your various suggestions. It was garaged for the winter then in the spring the throttle shafts and brake calipers were seized. Getting married and moving house meant that it got pushed into the corner and nothing got done with it.

I’m getting brakes sorted in next week or two (waiting for a caliper and some seals)

Compression I haven’t measured as the gauge I have doesn’t fit down the plug holes plus I had refitted the rad. Fuel is fresh from the garage last week. It’s possible it may be an air leak, I fitted new inlet boot clamps but the front one is a nightmare to get to. will try the WD40 trick to see. I don’t recall the misfire at idle before the bike was stored.

Cheers
Pete


Sent from my iPhone using Tapatalk

[R1ffR4ff]

Originally Posted by netsurfer

Will check your various suggestions. It was garaged for the winter then in the spring the throttle shafts and brake calipers were seized. Getting married and moving house meant that it got pushed into the corner and nothing got done with it.

I’m getting brakes sorted in next week or two (waiting for a caliper and some seals)

Compression I haven’t measured as the gauge I have doesn’t fit down the plug holes plus I had refitted the rad. Fuel is fresh from the garage last week. It’s possible it may be an air leak, I fitted new inlet boot clamps but the front one is a nightmare to get to. will try the WD40 trick to see. I don’t recall the misfire at idle before the bike was stored.

Cheers
Pete


Sent from my iPhone using Tapatalk

If you have not been riding for a while remember it's not just parts of the bike that might be Rusty!

Be safe out there

[netsurfer]

The problem seems to disappear somewhere between 3,000 and 4,000 rpm (when stationary, adjusting idle speed)

WD40 didn't seem to make any difference around intake boots or choke plungers but it's quite difficult to say for sure as the misfire is intermittent and the front boot is difficult to reach all the way around.

I have a feeling the issue could be on the front cylinder, the exhaust header (measured at the flange where it meets the head) is approx. 35 degrees (c) hotter than the rear. (no exhaust leaks anywhere on the system)

Would hate to do damage to valves from lean running, perhaps i'll pull the carbs again and put them in the sonic cleaner at work. Shooting in the dark I suppose but can't think of much else.

[maviczap]

Even my bike didn't run cleanly after I'd had the carbs sonically cleaned, after they got gummed up following a lay up. Like yours the front pot ran cooler, but once warmed up and running above idle it was fine. Won't hurt to give them another clean, but if it's running ok once hot. I wouldn't worry too much.

[Seeker]

did you check/set the air screws?

[netsurfer]

Originally Posted by Seeker

did you check/set the air screws?

Ah! Forgot!

I'll have a look later this evening. Spent the afternoon getting our digger going to dig out a blocked drain then midway through dug up the electrical supply to our bio digester so by the time I got that sorted i'm pretty wrecked!

Will update later

[R1ffR4ff]

Just to add.I've removed the central Horn bracket and moved my Horn to the Front left of my SV.This means I can get to my Front Spark plug without having to drain the coolant by just removing the 3 rad bolts and pushing the Rad forward,

The piece of card it a temporary hand and rad protector so I don't cut my hands or damage the Rad fins and is held in place with a little double sided tape and removed when I've finished work on the front

I've used new Racing NGK spark plug caps.These are often overlooked as a fault of ignition problems.Stock they read 5k ohms resistance.Anything north of 8 k ohms and they are suspect.I made some anti-crud/water seals from some old Inner-tube as the Stock seals wouldn't work with them and they are treated with ACF50.

https://www.ebay.co.uk/sch/i.html?_o...05FMR&_sacat=0

Too cheap not to replace IMHO.