1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Help Bloody zzr

Discussion in 'Kawasaki 250cc Twins' started by Martin Green, Feb 19, 2021.

  1. Martin Green

    Martin Green Member

    Messages:
    36
    Likes Received:
    12
    Trophy Points:
    18
    Joined:
    Dec 5, 2020
    Gender:
    Male
    Location:
    Canberra
    My Bike:
    Zxr250
    Hi

    you may remember I have been trying to resurrect this 91 zzr250.

    It now starts, idles, gets upto temp, remains at temp for 30 mins plus while stationary on the stand, so all good.

    However, I took it for a ride and out on the real roads I got about 10 mins away before it started stalling and then impossible to start.

    What are your thoughts?

    My immediate thought was charging system not able to give a decent thump, the battery is brand new but drained already.

    My other thought was valve adjustment incorrect. I checked them early on but its such a tight spot I wonder if I got it wrong. Could the valves be too tight and I'm losing compression when upto temp?

    I doubt this scenario as when I had it upto temp last night on the stand I rode it briefly and it was ace. It had been high idling for 30 mins last night, the fan had been on and off many times and the gauge was showing mid way for at least 25 mins so I feel that it was as hot as it needed to be to show a valve issue. It rode great just up and down the road then.

    If it starts easily once cooled down it must be valves right?

    thanks chaps
     
  2. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

    Messages:
    2,883
    Likes Received:
    1,489
    Trophy Points:
    823
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Location:
    Melbourne
    My Bike:
    Spada, VT250F & ZX2R
    My 2 cents...

    tough one to be 100% sure, but the fact it starts when it cools down discounts faulty R/R or charging system. If the battery was drained it wouldn't start.

    Might be a fuel starvation issue that abates after not running for a while. Something like a partial blockage of your fuel vent system? Or, a blockage in your fuel delivery system like an obstructed fuel filter or something similar?

    Your plugs aren't fowling otherwise it wouldn't start after a cool down. If it starts immediately after a cool down or at rest, then your plugs are in a healthy state

    Not sure about valve clearance either as they're pretty much up to heat as soon you start riding. Was your 10 minute ride at high revs or a combination of gears and revs?
     
    • Like Like x 1
    Last edited: Feb 19, 2021
  3. jmw76

    jmw76 Well-Known Member Premium Member

    Messages:
    592
    Likes Received:
    276
    Trophy Points:
    348
    Joined:
    Mar 12, 2017
    Gender:
    Male
    Location:
    Melbourne, Australia
    My Bike:
    Honda cbr250rr mc22 road + 1 track, Honda RC 162 tribute bike, Honda Spada Vt250, Honda CBR900RR
    Here is a left field thought.

    Have you checked the tank breather?????

    Maybe when you go on a decent run and start to use a bit of fuel it gets a fuel starvation issue.
    If the tank breather was blocked it would create a vacuum in the tank and progressively end up not feeding fuel to the carbs.

    Worth checking.
     
    • Agree Agree x 4
  4. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    Yes, try riding with gas cap open to test.
     
    • Like Like x 1
  5. Martin Green

    Martin Green Member

    Messages:
    36
    Likes Received:
    12
    Trophy Points:
    18
    Joined:
    Dec 5, 2020
    Gender:
    Male
    Location:
    Canberra
    My Bike:
    Zxr250
    Thanks so much guys.

    It does start again once cold but the battery was drained. The ride was a normal sensible shake down ride as its the first ride since recommissioning so I was being kind.

    Could it be incorrect spark plugs?

    I considered float height but feel it would be obvious after the first time I emptied the carbs with a squirt rather than ten mins into the ride.

    Weirdly, I have just finished an 88 vt250 and it seems to be doing the same thing. warms up fine, idles well, rides well for ten mins and then sputters and conks out. It also starts easily when cold.

    I'm pretty over pushing bikes home today!
     
    • Funny Funny x 1
    • Bummer Bummer x 1
  6. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    You're looking for something that changes over time 5-10 min.

    Incorrect spark-plugs would be wrong full-time. Any running problems from bad sparks would be present right from start, not 5-10 mins later.

    As mentioned, it could be fuel and vacuum-related. 5-10 min is about right amount of time for float-bowls to drain if you've got vacuum in tank that's reducing fuel-flow. To confirm, when it dies, immediately open float-bowl drain screws and see how much petrol flows. Collect into measuring cup and compare volumes in each float bowl if you want to be precise. If very little petrol drains, then you know you've got fuel-flow issue.

    I had similar issue on my EX250J race bike. It would idle and warm up just fine. But when I went out on track, it dies exactly 1-minute in (1/2-lap). Brought it back to pits and lift tank to take closer look, everything's fine. It idles and warms up for 5-10 minutes just fine. Went back out on track and exactly 1-minute in 1/2-lap it dies!!!

    Brought back in and took even closer look at all fuel-lines and vacuum-hoses aHAH!! I had made vacuum-line to petcock longer than normal for ease of installation. But it coiled up under tank and got squeezed between tank & frame when I lowered tank. This closed up petcock when I fitted tank. Dribble of flow was enough for idle and low-load use around pits. But when I went WOT on track, fuel-demands were at highest and one float-bowl worth of petrol was enough to get around 1/2-lap and that's it.
     
    • Informative Informative x 2
    Last edited: Feb 20, 2021
  7. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    Easiest test is to measure vacuum and fuel-flow rate from petcock:

    1. use rubber-T and connect to vacuum-hose at petcock
    2. idle engine and measure vacuum-level at petcock (this is very important measurement)
    3. disconnect vacuum-line from petcock and connect vacuum-pump directly to petcock
    4. disconnect fuel-line from carbs and aim into measuring cup.
    5. with vacuum-pump apply vacuum to petcock of exact amount measured in #2
    6. time 15-sec fuel-flow into measuring cup
    7. how much petrol flowed in 15-seconds? Multiply by 4x to get flow in l/min

    There's a number in manual that states minimum petrol-flow rate. Is yours at least this much or higher?
     
    • Informative Informative x 1
  8. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    Also verify float-bowl vents on each carb is clear. They need an atmospheric reference signal to apply 1-atm pressure to top of fuel in float-bowls. This pushes petrol out at calculated pressure based upon vacuum in carb-venturi. All finely designed and calibrated. Problem with vacuum or pressure side of fuel-circuits will cause issues.
     
  9. Brandon Otte

    Brandon Otte Active Member Premium Member

    Messages:
    197
    Likes Received:
    59
    Trophy Points:
    113
    Joined:
    Feb 29, 2020
    Gender:
    Male
    Occupation:
    Plumber
    Location:
    Hamilton, New Zealand
    My Bike:
    Yamaha FZR250 2KR ‘88 Yamaha FZR250R 3LN1 ‘89
    It sounds like my old lawn mower with a blocked fuel tank vent cap. Maybe try a ten minute ride with the fuel tank cap off - and a rag in its place to stop splashing? Otherwise what’s been said above^
     
  10. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    Rather than replacing entire bike one part at time (not economically efficient), try some measurements.

    1. what is voltage of battery with everything OFF?
    2. what is voltage of battery when cranking to start? Might need 3-4 hands for this. Or test-leads with alligator clips
    3. what is voltage of battery when idling?
    4. what is voltage of battery @ 5000rpm?

    These numbers tells tonnes more information about health of your charging system than we currently know.
     
    • Agree Agree x 1
  11. Martin Green

    Martin Green Member

    Messages:
    36
    Likes Received:
    12
    Trophy Points:
    18
    Joined:
    Dec 5, 2020
    Gender:
    Male
    Location:
    Canberra
    My Bike:
    Zxr250
    Thanks so much all, great info I appreciate your time in replying.

    I pulled the carbs again to check float heights, im still not convinced its fuel delivery due to being able to ride it for ten mins. I feel as if i'd have drained the carbs the first time I open it up and it would fail sooner but, hey, i love wrangling the carbs out of these things.
     
    • Funny Funny x 1
  12. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    Has nothing to do with float height.
    It's petrol flow from tank.
    If petrol is not flowing from tank, there's absolutely nothing float height can do to fix it.


    It's like trying to fill your tank from gas-pump that's turned off. You can try putting bike on its side, or removing tank from bike, or flipping it upside down. Doesn't matter. If pump is turned off, there's zero chance you're getting petrol.

    Let me ask you this:

    Where does the petrol live before it gets inside the carbs?
     
    • Like Like x 1
    • Agree Agree x 1
  13. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    any time carbs are cleaned, petcock should be tested, cleaned, and rebuilt if needed.
    if dried petrol gummed up carbs, it most likely is restricting petcock as well.
    Really need to measure flow-rate and determine a litre/min number to known for sure if petcock is flowing properly

    [​IMG]
     
    • Informative Informative x 1
  14. jmw76

    jmw76 Well-Known Member Premium Member

    Messages:
    592
    Likes Received:
    276
    Trophy Points:
    348
    Joined:
    Mar 12, 2017
    Gender:
    Male
    Location:
    Melbourne, Australia
    My Bike:
    Honda cbr250rr mc22 road + 1 track, Honda RC 162 tribute bike, Honda Spada Vt250, Honda CBR900RR
    Did you actually try running with petrol cap off or loosely fitted as suggested earlier?????
     
    • Like Like x 1
    • Agree Agree x 1
  15. Martin Green

    Martin Green Member

    Messages:
    36
    Likes Received:
    12
    Trophy Points:
    18
    Joined:
    Dec 5, 2020
    Gender:
    Male
    Location:
    Canberra
    My Bike:
    Zxr250
    I sure did try a run with the cap open. No better i'm afraid.

    I'll run the petcock through the ultra sonic cleaner too while i'm at it. And check all gaskets and connections.
     
  16. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    important thing in determining whether something is good or bad is to measure it and arrive at some numbers. Then compare those numbers with what's dictated in manual. Petcock can be cleaned 100000x and it will still be bad if it doesn't flow required minimum litre/min or litre/hr required to keep up with engine's consumption.

    just like with battery. we all know looking at battery does no good in determining if it's good or bad. Have to measure it to find some numbers to compare to a standard. BTW, you suspect charging system. Do those teststs outlined earlier to pinpoint or rule out if battery or charging system is at fault.
     
    • Agree Agree x 2
  17. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    for example, Is this battery good? How do you know? How would you know?
    [​IMG]
    is this petcock any good? How do you know? How would you know?
    [​IMG]

    In my case this petcock was both good AND bad!!! I was rebuilding my '86 VF500F and wanted to replace original vacuum-operated petcock with manual one. Lazy teenager didn't want to measure vacuum in hoses (5-min) and spent 5-days looking for petcock at breakers. Ok, so I found one! Thinking I was smart, I figured I'd "test" it before putting VF500F together.

    So, I put it on CB125T to find out. Both being Hondas of similar vintage, petcock fits on both tanks just fine. A 30-min ride on CB125T with frequent full-throttle bursts convinced me petcock was good. Put it on VF500F's tank and put bike back together. Went for test-ride, AHHhhh glorious! VF500F was running awesome, had more power with head-shaving and fully-radiused valve-seats.

    Then >pffttt< it stumbled a couple times and died! On side of road, I measured battery, full 13.5v, very good, I even disconnected headlight for extra umph. Crank, crank, crank, nothing. Sat there for 10min, scrathing my head, going over everything I touched from crank-bearings to valve-adjusters to switches, all assembled correctly. Gave it another cranki, it started right up and I rushed home. Just under 1km from home it died again!!!

    Pushing bike home, I went past Dougal's place. He was previous owner of Honda/Kawasaki dealership downtown who had retired couple years earlier. Guy must've been bored and missed the shop, because as soon as I was in front of his house, he ran out to see what's wrong. Told him what I had done and what bike was doing now. He said it was most likely fuel-related and to measure petcock's flow rate.

    Well darnit, being cocky teenager, I wasn't gonna let some old geezer tell me what to do! It took 5 more rides of it dying 5-miles out for me to think maybe he was onto something. I had ridden in opposite direction too so that I wouldn't run across him again! So I disconnect fuel hose frpm carbs and aimed it into measuring cup. Turned petcock on and measured petrol flow for 30-seconds....

    Looked up manual and whatcha know!!! Damn petcock flowed enough petrol in cc/min to run CB125T just fine, But was woefully inadequate for a 250 much less 500cc bike! I ended up completely disassembling that petcock and scraping out passages with screwdrivers and scrub-brushes. Removed tonnes of varnish and powdery crap that soaking never even touched in valve-mechanism.

    In 30-yrs since that incident, I automatically disassemble petcock and carbs on any used bike I get. Saves tonnes of time pushing bike back home! Here's good guide to rebuilding petcock: https://faq.ninja250.org/wiki/Rebuilding_the_petcock/fuel_tap
     
    • Like Like x 3
    • Informative Informative x 2
  18. Martin Green

    Martin Green Member

    Messages:
    36
    Likes Received:
    12
    Trophy Points:
    18
    Joined:
    Dec 5, 2020
    Gender:
    Male
    Location:
    Canberra
    My Bike:
    Zxr250
    Great story Danno thanks for taking the time to help.
    I haven't been back to the workshop since the suggestion so have not tested the flow but absolutely will first thing.
     
    • Like Like x 1
  19. Brandon Otte

    Brandon Otte Active Member Premium Member

    Messages:
    197
    Likes Received:
    59
    Trophy Points:
    113
    Joined:
    Feb 29, 2020
    Gender:
    Male
    Occupation:
    Plumber
    Location:
    Hamilton, New Zealand
    My Bike:
    Yamaha FZR250 2KR ‘88 Yamaha FZR250R 3LN1 ‘89
    @DannoXYZ does that apply to the Yamaha petcocks?
     
  20. DannoXYZ

    DannoXYZ Well-Known Member

    Messages:
    168
    Likes Received:
    78
    Trophy Points:
    228
    Joined:
    Sep 7, 2017
    Occupation:
    IT Manager
    Location:
    S.F. Bay Area
    My Bike:
    Honda CB125TT, Kawi EX250E, EX250F, EX250J street, EX250J race, Honda CBR250RR-MC19, CBR250RR-MC22, NSR250R-MC21 VF500F, CBR600RR, VFR750F
    Yup, many Yamahas use same petcock as Kawasaki. Judging from how they use same rebuild kits: https://www.amazon.com/dp/B00ANSVW5Q

    All modern vacuum-operated petcocks are similar with vacuum diaphragm and plunger that blocks flow passage. As with carbs, spray cleaners no longer work due to removal of chlorinated compounds. If you haven't disassembled petcock to this level, you haven't gone far enough. In gneral, I always order rebuild kit and rebuild petcock as it takes same amount of time as opening one up to clean.

    [​IMG]
    [​IMG]

    1. most common issue is blockage due to dried petrol and corrosion (white powder). This will limit flow even with fully-operational petcock with sealing rubbers. You'll want to scrub all passages from beginning to end and remove all dried petrol varnish and corrosion with scrub-brushes and solvent. I like using acetone, PB-blaster or 50/50 blend of acetone/ATF. Use some rubber-grease on mating surfaces when re-assembling. Don't forget greasing bevel-spring on front side.

    2. Another common problem is leakage at vacuum-diaphragm from tears, holes or cracks. This is determined by vacuum-test with pump & gauge outlined above. Vacuum-leak presents as higher vacuum needed to start petrol flow, +20 in.Hg (-33 kPa). And vacuum won't be maintained to keep flow moving. You'll have to keep on pumping additional vacuum to diaphragm to keep it open. Working diaphragm requires just one pump, then stays open and flows petrol indefinitely.

    3. yet another issue is leaking plunger that doesn't stop petrol flow even though vacuum-daphragm is deactivated. This can be caused by worn-out spring and/or plunger O-ring. This causes petrol to dribble into your carbs even though bike's not running and petcock turned to OFF. Due to state of disrepair, float-valves in carbs most likely not operational and petrol fills up float-bowl and drips down carb-throat into engine. Where it sneaks past rings and fill up crankcase with petrol. Depending how bad leak is and how long bike sits, you may have hydrolocked engine without riding through river!!
     
    • Like Like x 1
    • Informative Informative x 1

Share This Page