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New bike?

Discussion in 'Bike Reviews, Questions and Suggestions' started by cb rookie, Aug 19, 2011.

  1. So i bought a 95 CB400, and after getting approval from 2 mechanics, I thought it was all good to go. About a month later, its broken down twice (first time had the carbs cleaned, it was full of water, one cylinder wasnt getting fuel, etc.)

    the second time was the other day - both times it just started losing power when riding, then wouldn't pickup at all when i turned the throttle.

    I suspect it's had a pre-existing compression issue, as in 6th gear on the highway, the revs are at 11-12k, with the speedo reading 130 - This is just keeping up with highway speeds. It would seem that the cheap chinese speedo the original owner put on it is shite, and way out. I drove beside my mate in an 80 zone - the bike read at 95-100.:censored::censored: So long story short, Im wondering if its a compression issue?

    Now the bike is at my mechanics place, and he's gonna compression test it and yadda yadda, but he reckons the break downs are fuel related eg carbs.:nail:

    Now, it is obvious i made a noob mistake in the first place by buying it. Obviously the best course of action at this stage is to wait and see what the mechanic says. But if the compression is rooted, I'm under the impression that even finding the issue can be an expensive process?

    I thought I'd come here before making yet another n00b error of judgement :WStupid: If this bike will be expensives to repair, i was thinking of going and buying a demo cb400. I've ridden good working CBs before, and i love them, so i'm sure this would outlast my LAMS and further (I can get my open in may next year :S)

    I was undecided, but while this initial bike was functioning (albeit quite poorly - and because it was poorly), I was thinking of saving for a street triple or daytona after i get my open licence (despite the fact i would have been coming off a bike that was severely speed impaired.

    I probably should've added earlier that I would like to use the bike for highway riding, though I find the naked (no protection) bike fine at those speeds.

    Anyways, I'd appreciate any advice, ideas, reassurance :D

    (Sorry for the jumbled post)
  2. Man, that sucks! Especially after two grease monkeys gave it the all clear. I'd have bought it as well after that!

    Did you know the original two mechanics, or were they 'independant' of the place you bought the bike?
  3. Hello Rookie, nice to meet you.

    It's a little hard to give good advice because I don't actually know what the issue is. (With the engine. Chinese instruments are their own reward, so that's different.) I'm wondering where you get your fuel, because it sounds to me like you picked up a load of water and crap, and then after it was all cleaned out you went and did it again. I could be wrong but that's my first instinct. A new bike won't fix that one.

    Is it worth getting a new 400 and then shortly afterwards getting a Trip? Well sure, if you can afford it. I think you'd drop a heap of dough and not get very good value for money, myself, but that's just my opinion.

    Major suggestion - wait and see what the spanner twiddling man says first. If there's crap in the carbs and the fuel again, don't blame the bike - blame the service station where you picked up a (second) load of bad fuel. Fit a big car type clear plastic fuel filter that sits where you can see it and watch for water contamination, and buy your fuel at a big, busy service station, preferably a reasonably new one. Perhaps throw a bottle of fuel system cleaner through it every couple of months.

    If the compression is bad, there are a number of things that can cause it. Some are quick to diagnose and some are not. Some are easy to fix (as long as they're picked up early) and some are not. It rather depends on what's leaking.

    Do your carbs have drain screws? Back them out and drain the carbs and try it. 30 second job. ... looking for a good simple diagram - harder to find than I thought...
  4. Big W - Yeah, the mechanics were independent. I bought the bike in a private sale, no dealer. It has had a slide on the ground (from previous owner), dunno if that has much of an impact, but i guess you'd need to open it up to determine that. The first mechanic does my cars normally, but he used to work on/rebuild racing bikes. The second mechanic (whose been sorting out the current issues) was a referral from my first one, as he'd be able to take it for a test ride for me as well (a noob wouldn't pick up some of the finer warning signs) ( i test rode it too, and it seemed good).

    Kneedragon - Thanks mate, you too.
    I was thinking that if i ended up going the new cb400 i'd scrap the triumph plans for a few years, so hopefully (and given the poor performance of the current bike), a brand newy would wow me for a good while.

    I wondered about fuel, but I've always got my car fuel from there. It's a 24hr, shell/coles-on-a-main-road job. never had any issues there before. The first time it died like this (on the higway) i was running normal octane unleaded (95?), but after i got it fixed up, I've been only running premiums (i read hear that jap has 100ron petrol, so 98 is the closest thing + premium = better for most bikes). The reason i'm so concerned about compression is because the revs are ridiculously high for the speed. I have considered that maybe i'm expecting a bit much from an older bike, but in 1st, it barely gets to 25 before redlining, and now i know that it's actually a lower speed (re: speedo inaccuracy). Especially seeing as I learnt on a 1992 cb400 (that had been pranged relentlessly) and it got to quite impressive speeds in first, and other gears. I know the redline on my cheap-china speedo is relatively accurate though.

    I'm by no means a mechanic, and the thought of touching any screw on the engine/mechanical parts induces thoughts of totally ruining it, i'm sure the mechanic will have a look at that part for me anyway. sounds like he's gonna have a thorough look at the carbs. but the float bowl was full of water last time.

    I should add that the mechanic thought it sounded like a fuel thing again this time, but IMO/reasoning-without-mechanical know-how, I thought a fuel problem wouldn't cause the revs to be high with such low power output as the fuel is what makes the revs get that high? therefore, (when it's running) would it not be a case that fuel flow is fine for the revs to be that high? (Im genuinely interested in that one). but compression would mean it would need higher revs just to get a lower output?
  5. What state is the clutch in? Lots of revs and not much speed (assuming the gearing is original) could be a slipping clutch. Simple test for how well the plates bite is to ride it at a steady throttle setting in top gear, and very quickly pull the lever in and release it. A good clutch will re-engage immediately, a worn clutch will take a second or two to regain correct tension. Poor compression often shows up in other ways, like excessive oil in the breathers and oil in the airbox, assuming the crankcase breather is still routed there. If the compression is too low, the engine will struggle to start.
  6. Rookie, this is a bit of a can of worms, and I'm wary about getting into it right now.

    Like the bumblebee man says, a slipping clutch sounds like a possibility here.

    Changing (losing) compression will not have any effect on what revs the engine is doing at a particular road speed. A slipping clutch, wildly inaccurate instruments, or an engine with a very different feel (that feels / sounds to you like it's revving twice as fast as it really is, f'rinstance) could all be candidates here.

    Water in the fuel will cause the bike to stop running, perhaps just on the one pot that has water... Would you know what it felt / sounded like when running one cylinder down?

    What-ever. I reckon let the mechanic fix it. Ask him to explain what it was, and ask questions until you understand what that means. Keep the dunger (once it's running properly) and save your pennies and shillings for a new Triple when the time comes. I think you'll be happier. I also think new riders have little slips and mishaps. That doesn't have to a crash - it can be 'My foot slipped on the wet grass!' Things like that happen a lot more when you're starting out, because out haven't learned all the traps yet. A few small scratches on a well worn dunger is no big deal. Dropping your brand new $16k (?) Triple in your driveway and doing $6k worth of damage to it in the first hour has got to hurt. I watched a friend (Hello James) drop his brand new honda CBR600 twice in an hour - once at walking pace on the right and once at about 50k on the left. Then it slid under a guard rail. It can happen.

    [Edit] Hold the phone - I know what it is!

    *** Check the air filter.***

    If I had $50 bucks I'd bet when the bike's fallen down oil has run up through the crankcase breather and flooded the airbox, and clogged the hell out of the air filter. That would explain everything. Get your mechanic to check it and have a new one there ready to go in. Wipe out the airbox with a clean rag, change the air filter, drain the carbs, and take it for a spin and see how it goes.

    Note: Bad rings and poor compression can also flood the airbox and filter with oil, but the bike has fallen down, and an airbox full of oil could more easily come from that than from bad rings and blow-by. Don't go fixing (at great expense) problems that don't exist.
  7. Check the carby rubbers from the manifold for air leaks this also will make a bike run like shit.
  8. Compression -
    When your mechanic does the compression test, he'll pull the plugs, test and write down the results.
    Then put a teaspoon of oil into the cylinders through the plug holes and Retest If the compression goes up, rings are worn, if it doesnt move, valve leak. If the readings vary by roughly 20%, there is a fault with the low cylinder, if theyre all within about 10%, its normal? wear and tear.
    either way if its too low its a top end rebuild, and unless the guy has a camera he can put down the bore you wont know if the cylinder is scored until you get it apart, he still wont know if its rings or a a rebore until he can measure everything.
    Your mechanic knows all this, just hasnt been into it with you yet.
    Damage will depend on how far the bikes gone and how well its been treated.
    Personally, I'd price all the parts first and get a rough idea of worst and best case total costs before you get someone to pull the motor down. How bad does it have to get before you cant live with it?
  9. Bee - We initially wondered about the clutch, but he had a quick glance at the (outside casing?), and it looked like the seal was newish, so he didnt bother pulling it off, he did adjust the lever on clutch though (on the handlebars). I wouldnt have thought thats the issue (or maybe it is), but when i start it and put it in gear, it has stalled before, as thought the clutch wasn't in at all, when the lever was fully depressed. so IDK about that? Sometimes the bike really struggles to start, but i think thats more to do with how cold it is, cos if it's been in the sun its not so bad
    P.S the choke stalls the bike no matter how cold the morning, or how warm the engine is. again, may have something to do with poor starts as can't use the choke.

    Dragon -Im not sure about not having one cylinder functioning, but last time my mech had a look, he said one of the carbs was blocked (i assume this means no fuel = no cylinder?)

    I totally agree about keeping it and persevering until im off restrictions, but my motivation to do this wavered after it stopped again with the symptoms of fuel loss. I am very reluctant to by a brand new bike (cb400) atm, because as you said, one drop and you'd think "why'd I bother?"
    Not to mention that a triple would probably be more satisfying than a CB400 in the longer run. Mind you, i did drop this bike in my driveway trying to get it on the centre-stand. onto cardboard, with (aesthetically) no damage to the naked eye. this could have compounded the oil in air filter deal, because fuel leaked out of a hose that was connected to nothing (overflow?).

    Z900 - I'll probably ask him about that also.

    Foot - Yeah, I'll see what the mech says i spose. It's pretty clear im a mechanical gumby, so i'll call him up this arvo and see what he says.

    Thanks for all the feedback guys! Really appreicate it. I'll try and get onto him over the next few days, and if he's stumped, i'll offload this info onto him (or if he hasn't mentioned any of it either :p)

    I'll update with any progress on the issue (including resolution)
  10. There's bike mechanics and there's bike mechanics. Hope you've got one of the good ones. Is there a filter on the fuel line? Old bikes get crud in the bottom of the tank that finishes up in the carbs if it gets stirred up. Might be worth checking the electrics as well. Looking at the spark plugs can give clues as to what's happening in there. Anyway a good mechanic will go through all that. If the engine is stuffed you might be able to get a replacement or rebuild it?
  11. So an update! The mech called me over the weekend and told me the bike was good to go. He told me that when he went to do the compression test, the spark plugs were really loose, and one of them was about to come off by itself :S He also found that there was an issue in the fuel tap -the spring was keeping the diapraghm shut, making it hard for fuel to flow properly. but he got it on the highway and said it was running better than before (revs - speed).

    After picking it up, I got about a km from his place, and it died on the main drag, same symptoms. after some swearing, i called him up and he cmae and had a look. We knew the fuel tap should be fine, so he pulled the fuel hose off of the tap, and nothing came out. we were perplexed for a bit, then he opened the tank cap, and fuel came out like a waterfall. so after promptly closing the cap, and the fuel flow stopping almost immediately, we concluded that there was no vent in the tank cap.

    Cue flashback - When i first saw the bike, the guy selling it had a massive ding on the fuel tank. He ordered one off ebay, but it came without the key for the tank cap. By this stage i was getting pretty close to buying it. He emailed the guy from whom the tank was purchased, and was advised that the key would arrive in a few days. so the brainiac selling feels this is too long, shatters the pins in the lock on the new tank's cap, and replaces it with the one from the old tank (which obviously is slightly different in either size or compatibility).

    Currently, the bike is with the mech, and after having dropped off the old dinted tank, he's gonna play around and see what workaround/resolution can be done.

    Twist, the electrics were all checked initially, as we thought that could've been an issue.

    And the cost of rebuilding/replacing the engine would be so high that it would probably nearly be more cost-effective (not cheaper) to buy a newer bike.

    Will update when i get the bike back again. May end up selling it to someone as a project bike.
  12. So!

    Got the bike back last night, running as good as when i got her. The problem was the suction in the tank, after a while the pressure built up and prevented fuel flow. He fiddled with the alignment of the breather, and hopefully should be right from now on.

    I also found someone who wants to buy it - my boss. He's a great bloke, and he's my boss, so i ran him through all the issues so at least he can't sy i sprung anything on him.

    He's only looking to spend about 2k, so its probably one of the only things he could get anyway. He's getting his licence on saturday. Providing all goes well, i'll sell that and upgrade to a brand new'n.

    Ironically, my mechanic is looking at buying one as well :p