Ex-500.com - The home of the Kawasaki EX500 / Ninja 500R banner
1 - 8 of 8 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hi all,
My bike started bogging a couple of weeks after adjusting the valve clearences. Worried that i may have messed somthing up i have just done a compression test and compression is low at about 115psi on both cylinders (acceptable range 128 - 196) but a wet test brings them back up to around 145psi so i dont think it's the valves. If it is the piston rings, why would both sets have failed at the same time? I repeated the test 3 times to ensure the results weren't a flook, there was some variation after adding oil to the cylinders but all results were between 140 and 150 psi. Could wet test results change if it's a failed head gasket? Any advice to further diagnose the problem would be appreciated. If i can avoid a leak down test that would be great as i don't have the equipment for that.
Thanks in advance.
 

·
Registered
Joined
·
2,597 Posts
age, mileage of bike Maintenace history is useful missing info. how was it running before/after the valves were done, any other symptoms fuel in oil, coolant in oil, coolant loss, oil level ok when last changed, how was/is it running overheating/under cooling all may be relevant to your issue.
how long since the last carb service for instance, as a general rule bogging is a symptom of fuel/carb issues but can also be down to vacuum leaks poor valve adjustment or even exhaust leaks all need to be checked as once you start to strip down the engine other issues need to be addressed (don't worry about that just for now).
while everyone's experience with this bike may be different but common issues do occur.
my point is slightly low compression would not by itself make the bike a non/poor runner for instance my 1990 gen 1 has 89k on it, yes, the engine is well worn (comps are around 125psi) rattles like a can of bearings (when cold) but still starts and runs just fine because everything else on the bike is perfectly set up,
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 · (Edited)
The bike is 1995 but only 25000 miles, it had sat in a garage for a little over 10 years before i was given it. It had a full service history before that. When I got it I changed the oil, filters, spark plugs, coolant, cleaned and balanced the carbs and replaced the jets, also replaced the petcock, fule line and vacuum hose. It started running pretty good after that.. I checked the valve clearences because they were due, they were a little out of spec (on the tight side) so i did the necerssary adjustments. The bike ran fine for a couple of weeks but then after running for a while it started bogging at higher revs and would stall while idling. Now it's hard to start, sometimes it will idle for a bit but then stalls. It wasn't over heating the oil colour is as expected and coolant level hasn't dropped. I have checked for vacuum leaks by spraying carb cleaner around all the obvious places and no noticable change in revs, but then there is only a slight change when spray directly into the air box so not sure how to check more accuately while its running so poorly. However the rubber boots either side of the carbs are still in pretty good condition no cracks fairly supple and seem to give a good seal. Then I thought maybe it was running a little rich so checked the spark plugs 1 was black, both sparkplugs still seem to give a good spark when tested. I tried adjusting the idle screw 1/4 turn in both directions but no change in symptoms. Thats when I did the compression test. The engine was slightly seized when i got it, it took a little persuasion with engine oil and rocking it back and forth to get it to turn all the way over.

Thank you for your reply.
 

·
Administrator
07 Ducati SS800 '95 Ducati 900SS/SP '19 Honda CBR650R
Joined
·
16,309 Posts
bogging at higher revs and would stall while idling. Now it's hard to start, sometimes it will idle for a bit but then stalls.
Sure sounds like carb issues to me. Also suggest reviewing petcock function and consider flapper valve removal as well.
 

·
Fast Old Guy
Joined
·
20,072 Posts
Low compression is just that. Not caused by external factors. In you case and all cases with similar ctedt results ,you rings are worn. Your statement that the engine was slightly seized is the tip-off. The rings we’re frozen into the bores and we’re damaged whe you broke them loose.
then some running wore off the rust and the comp loss resulted.
The only fix is new rings and a cylinder re hone.
in my opinion @ 25k miles you agotton the full lifespan of this engine.
run it as is fix it, of junk it.

Fog
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #6 ·
It's not the petcock because it behaves the same when connected to an auxiliary fuel tank. However I will check the fuel level in the float bowls. Where are the flapper valves I tried googling it and came up empty. Thanks.
 

·
Administrator
07 Ducati SS800 '95 Ducati 900SS/SP '19 Honda CBR650R
Joined
·
16,309 Posts
inside the fuel cap, affect tank venting
 

·
Registered
Joined
·
48 Posts
 
1 - 8 of 8 Posts
Top