Battery weak in cold weather?

It's a little on the cold side in London and I'm having to take my battery out whenever I leave the bike and keep it somewhere warmer otherwise the voltage drops so much that the bike won't start. Usually battery is at 13.4 V but if left in bike goes down to 12.8 V. It is a Lucas battery YT12ABS 12V 9.5AH. Does anybody else have this problem?

I'm going to rigorously test the reg/rec and alternator this weekend but I don't think it's the problem. At highish revs (5000rpm) the voltage is around 13.8V so don't think it's that. Also the fact that the bike starts if the battery is kept somewhere warmer and stays at 13.4 V makes me think that it's getting charged along the way.

I also have a different problem (get everything done in one post). Starting my bike in the morning I get soo much backfire, both in exhaust and in carb. This is my first SV and it hadn't been run for a year so I had cleaned up the tank, fuel lines and carbs to get it going, with new spark plugs. I can't figure out why it pops soo much in the morning. It rarely pops when it warms up but if it gets too hot, e.g. in heavy London traffic it will do one big pop in the carb and the bike will die. Anyone know if this is a bad problem or if there's a solution would be very much appreciated.

[rictus01]

Firstly, the bike should start fine (charge wise) with 12.5v or above, I've known bike start on as little as 11.8, but that's not your worry, it's ampage, if your battery is old or been abused to the point of runing totally flat, then it may appear to charge fine, but will have little in the way of reserve it it fails to catch first time, I know of no battery in good condition that requires removing from the vehicle to "keep warm" in fact I just changed mine even though it appeared to work fine (8 years old) and I'm in London to, so cold as here.

secondly (and this could be related to the first), the bike obviously has difficulties starting, this maybe something a s basic as a dirty air filter, carb balance or exhaust/vaccum leak, or down to jetting/ stuck choke plunger,water in the carbs, coil breakdown or feed, without proper diagnosis it's pretty hard to tell from your description.

Sounds like you need to get some of the basics checked/serviced, in order to track down the cause.

Cheers Mark.

[andrewsmith]

How old is the battery? That is the cause by the sounds of it.

The carbs sound like they also need a clean inside the bowls and the jets. Good service will cure probably all of it. Spanner Man (Stewarts Motorcycles) is really good, or put a shout in the Soho Massive section and someone might be able to help

Edit: Mark beat me to it!

I'm more inclined to believe it's a crappy battery, just the guy I bought the bike from had said it was brand new and I was hoping he wasn't lying. I'll check the reg/rec just to be sure but it seems like I'm buying a new battery.

In terms of starting, the bike catches quite quickly even when it's freezing cold, just needs to be at 13.4 V for the engine to be turning fast enough so that it would catch. I was (and am) surprised that it has to be so high on this bike considering everyone else on the forum seems to be talking about 12.X V. I should probably check for current leakage as well just to be sure. I have had the carbs cleaned (about 2-3 weeks ago now) but didn't balance them or synch them. I cleaned the air filter and have cleaned and lubed the choke plungers which seem to be working fine.

[yorkie_chris]

I bet if you looked in that battery it would be sulphated to death. If it is slowly being drained... like if charging system is weak at low (cruise...) revs with lights on, this can do it.

Check charging system and change battery.

[Sir Trev]

Originally Posted by Funky Munky

I have had the carbs cleaned (about 2-3 weeks ago now) but didn't balance them or synch them. I cleaned the air filter and have cleaned and lubed the choke plungers which seem to be working fine.

Did you do the carbs yourself? Did you take them off and reinstall them yourself? Not too clear from above. If they've been well cleaned through and especially if they've been off and it's been sat for a year you need to get it all balanced. Check for air leak too to make sure they're seated right.

Wehn you say you cleaned the air filter - how did you do this? The standard one is paper so you'd be better off replacing it. They're not expensive and if you've gone to the trouble of cleaning the carbs and adding new plugs it makes sense to be doubly sure.

You don't say which bit of London you're in. Spannerman is in Sunbury if that's convenient to you. He'll sort it all out for you and/or show what needs doing as he's a top bloke.

I took the carbs off myself and cleaned them AND took them to the shop to get cleaned (off the bike). The idle screws were seized in and I couldn't get them out to clean the idle jets so they cleaned it for me (screws still seized). I put them back on without balancing or synching (as I can't get at the idle screws). I don't have any air leaks from checking by putting my hand around any air flow through the carb and it pulls a lot of air through the carb hole so I think I'm happyish with that. I cleaned the air filter with compressed air. The bike's only done 25000 miles and the air filter is white so I didn't replace it, probably should though as you said seeing as I've gone to the trouble of all the other service.

I'm new to the forum so I'm still not very aware of this Spannerman. I'm in north central London (Holloway), would be a nice ride over to Sunbury. I went to the local shop and was going to do a load test but when I explained all the symptoms he just told me to change the battery. Gonna do that then if it doesn't work I guess I've got a nice ride to Sunbury.

[yorkie_chris]

You don't use the idle screws to balance the carbs.

Sorry, I meant something different but I don't know what it's called when you adjust the idle screws individually until the bike runs good.

[yorkie_chris]

There's a balancing screw on the linkage, sticking up at rear left of carbs. These can get a bit sticky but are easy to free off (steel in steel, no dramas)
Usual ones to seize up are the mixture screws which are underneath the carbs, these are brass into pot metal/cast zinc and can be a nightmare.

By the way if you do take bike to Stewarts he is one of the most knowledgeable guys I know, definitely recommended.