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Bike engine not smooth sounding at idle

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by SaneForest, Jan 16, 2012.

  1. Hi all,

    I've got a Suzuki Intruder VL250, bought second hand, 2007 model, 11,000km on the clock.

    A bit of background info. I've only had the bike a month or two and it's fine to ride, no problems stalling at lights or anything, but haven't taken it in to a mechanic as I'd really like to learn how to do it all myself.

    The bike wasn't in great condition when I got it and not sure when or even if it was serviced at all. But after checking the oil, brakes, and chain, it would seem it's not been taken care of too well. Brake fluid was black, oil was black and chain was also black (not a lick of silver to be seen, completely covered in sticky greasy dirt stuffs). I cleaned the chain, changed oil and brake fluid and front brake pads too.

    Apart from that I noticed the bike engine doesn't sound smooth, but I wouldn't know where to start to diagnose something like this. It seems to idle just fine but doesn't sound quite right. It's hard to describe but it sounds like the engine gets a touch faster for a few chugs then back to idle.

    To help out I recorded and mp3 of what it sounds like, not sure if it will help or not or if you can hear what I’m talking about.

    Any help greatly appreciated.

  2. V Twins always sound a bit lumpy. If it rides Ok, starts Ok when it is cold and doesn't stall when it idles then it is probably OK. You don't mention the air filter in your work, maybe worth checking considering the other maintenance items were neglected.
  3. Thanks cjvfr. This is my first bike it's hard to know what it should sound like. But that puts my mind at rest.

    Yeah, I was planning on doing the air filter next, along with learning how to do valve clearances, clean/adjust the carb, and whatever else seems simple enough to for a beginner to do.

    For the air filter my manual (workshop manual) says to clean in non-flammable solvent. I'd have no idea what to use as my first thoughts would be methylated spirits or something like it. I've heard of people just using dish washing liquid but I wouldn't know if thats okay or not.
  4. change the oil filter? when you adjust the chain ont over do it, you got a manual?
  5. I changed the oil filter and it's o-ring along with the sump plug crush washer too. Everything accounted for :) Grabbed a new set of spark plugs too. The old ones were very black and sooty on the end. I don't know what really causes this or how to fix it, still working it out.

    Yes, I have the workshop manual and the owners manual that came with the bike.
  6. As said above, V-twins are inherently a bit uneven. However, assuming it has twin carburettors, a carby balance probably wouldn't do any harm.
  7. Ther idle just sounds a bit slow, but the uneven running might be worsened by a clogged air cleaner, plus your description of the state of the other stuff could point to crap/water in carbs (a quick drain of the bowls underneath and maybe some fuel system cleaner in a full tank might help).

    Also, unless that model runs a single carb, then a pair (or more) needs occasional balancing. It might also be worth checking that the idle mixture screw adjustment is set where it's supposed to be, whether it's single or two carbs.

    Also, just a personal thing: Avoid ethanol blend fuels if not 91 RON outright, at least for the time being, just to take another possible variable out of the equation. The difference in cost to better fuel in a 250 amounts to maybe 50 cents a week. Any of the big brand 95 fuels is usually a safe bet.

    Aside from all that, most which is easy enough to do and not a bad idea as part of a routine checkup, a slightly uneven idle isn't especially uncommon, but again, see what you're idle is at now and if it's set where it's supposed to be. Somewhere within 1200-1500 rpm covers most bikes.
  8. It's a single carb. I don't know a lot about carbs, I get how it works (mostly) but wouldn't know where to find the idle mixture screw or adjust it without a bit of instruction. Will check the workshop manual and see if that helps. It's a mikuni bds carb if anyone knows a bit about that and where I should be looking.

    I haven't got a tachometer to check idle with, but I will probably get one so I can get things right. Wouldn't know how to get it right by ear till I had some more experience.

    I'm in tasmania and haven't really seen many servo's around that sell the ethanol fuel, not sure it's all that popular down here. I mostly fill up on regular 91 at woolworths/caltex servos. Never seen the ethanol fuel at these though.

    I'll clean the air filters tomorrow then I'll get stuck into to learning about this carbie.

    Will do as recommended and drain the bowls and grab some fuel cleaner too. Maybe it's worth replacing the fuel filter too?

    Thanks (everyone!) for all the great info, very much appreciated! Very helpful community here.