Kawasaki Motorcycle Forums banner
1 - 20 of 24 Posts

·
2storke god 4stroke nub
Joined
·
26 Posts
Discussion Starter · #1 ·
i got a h1 750 zxr it has backfired since i got it ive cleaned the carbs and got floats set up seems to overfuel starts ok on choke as it warms itl work no choke on
jenraly runs ok accept it stutters backfires wich comes wrong way down carb and sends a flame out the exhaust it gets worse as i open the throtle but i can get a high rpm from it with it splutering at me and burnt debri flys out the zorst it seems to me it culd be

valves not closeing fully allowing fire bk down to the carb but this dont explain the flames out the zorst end

incorect timeing sparking before the carb valves close but bike runs shuld it run ??

bad computer causeing timeing out on 1 plug
or 2
feel free to ask questions

all plugs fire fine there is fuel and air i cant sync properly till bk fire sorted but it has been done to eye on bench

bike was bought n bumped it ran straight off but then overfueled as carbs un blocked i set up the floats to resulve this bike sounds rough as heck seems to be a lot of noise from i think valves like no oil at all but cant hear properly coz of the bk fireing hopefully u understand what im trying to explain and can offer a sugestion or 2
 

·
itching to ride
Joined
·
2,238 Posts
Not exactly but it seems you are saying you are getting a lot of backfire as if the timing is off but it runs so how is this possible. Is that about it?

Have you checked the valve clearances? If you have a tight valve or valves you can get conditions like this. I would check that first before messing with the carbs or anything else. Check and adjust as needed then post back.
 

·
2storke god 4stroke nub
Joined
·
26 Posts
Discussion Starter · #7 ·
my apoligy my speling is rubish and im not good at explaining things let me try again

i bought the bike a year n half ago.
when i got it home i bump started it as it had no battery .
took a bit of pushing but it started up fine with the odd backfire but it rode fine
for a whyle ..
i rode it down the road and the backfireing got worse the engine became weak too weak to even take off on its own power.
after runing 5 minuits it then dies unless u put it on full choke wich buys you a few minuits of extra engine running time and power is slightly restored . and it then refuses to start for a good 20 mins +
i could smell petrol badly it was obviously overfueling i knew it wasnt overheating so i cleaned the carbs out set all up to factory standard no change .
tryed smaller jets this made a change it came with 1.28 size main jet i tryed going down to 1.00 this made it more reliable slightly but the backfireing still there after a short run it starts playing up again and i culd only get half throtle coz of the lack of fuel i asume .
so i moved up to 1.15 it still seemed to over fuel but not as bad .
still backfireing and dieing after a few mins ride
carbs are curently 1.28 wich is factory standard floats 14mm factory standard is 13 give or take 2 mm
carbs are spotlessly clean all set to factory standard i kno they are ok tho prehaps out of sync slightly ive syncronised the carbs by eye on a bench but not with vacume gauges as yet as it isnt running well enough +im too poor to buy the gauges at the moment .

when it backfires it pops in the carb and the exhaust flames also come out the exhaust accompanyed by small flakes of burning carbon

ive checked all ht leads and they are fine.
ive gone through 5 sets of new spark plugs
plugs are accumulateing black carbon fast
the bike has backfired since i got it but seems to be getting worse vertualy constant bang pop pop pop bang
the best ive known it to run is before i cleaned the carbs when the gel like petrol that had been in there was restricting the flow of fuel .
that was till it ran fast and sucked all the crud through the carbs thats when it realy started playing up wich made me clean the carbs
if i can get the backfireing to stop i would have a better idea of what i need to do fuel air wize .
im pretty stumped this is my first 4 stroke i kno a fair bit but not enough

i think that explains it >.>
 

·
2storke god 4stroke nub
Joined
·
26 Posts
Discussion Starter · #8 ·
checking valves is my next job as it dont seem to be the carb im thinking pull the engine out take off head check valves and pistons new gaskets anywhere i go

im dreading touching that timeing chain i kno if it dont go on exactly right im in s**t or god forbid it falls down in to bottom end and i gota do a full strip to retreave it
 

·
itching to ride
Joined
·
2,238 Posts
No no no. I meant check the valve lash. You do not need to pull the engine to do that. It sounds like you have more than one valve that is tight. I would advise against running it any more until you set the valve clearance. You need a service manual so you can see how this is done or take it to someone who knows how. You will have to pull the valve cover off and check the valves to see if you have adequate clearance.
 

·
Registered
Joined
·
1,342 Posts
"i bought the bike a year n half ago.
when i got it home i bump started it as it had no battery .
took a bit of pushing but it started up fine with the odd backfire but it rode fine
for a whyle .".


did you put a new fresh battery in the bike or not or are you still pushin the machine to start it? a bad battery or no battery will cause lack of voltage to the coils and foul them plugs quickly.and if you have changed the battery is it chargeing the battery @13.5 v plus? may have fried the rectifier running the machine with no battery.just a thought.
 

·
Navy Vet Search & Rescue
Joined
·
8,843 Posts
In addition to the advice already given, I'd check the fuel tank vent to make sure it's not clogged. That will give the run for xx minutes then stall and not restart for 20 or so minutes type problems. Since it sounds like it's firing on partially open valves, if the valve clearance is good, check the auto timing advancer if the bike has one (I'm not sure what year model the h1 is).
 

·
itching to ride
Joined
·
2,238 Posts
I believe the H1 is the 87 year model. I checked kawasaki.com yesterday to see if he had screw lash adjusters or shims and he has the shims under bucket. But I am not for sure what year it was. It was either 86 or 87, I am pretty sure. But I do not feel like rechecking as it really does not matter.
 

·
2storke god 4stroke nub
Joined
·
26 Posts
Discussion Starter · #13 ·
in answer to the questions

new battery installed before 2nd runing bike starts on battery

the bike is a 1989 h1 model with shims and bucket

the flow of fuel is good no problems there tho it seems the previous owner removed the fuel pump i dont kno why but it has been bypassed surely that only effects high speed runing if anything

the bike ran well when it had blocked up carbs other then the back fire

i have the haynes manual on pdf

the clearence on valves shuld be
intake 0.15 to 0.24
ex o.20 to 0.29

ive not looked yet as i need to buy the guage
the reason i think it would be a god idea to take the head off it to
1 to check pistons are in good condition
2 check amount of carbon and clean
3 ensure that valves are not stuck in a slightly open position by carbon or ware and get sum laping grease on them if nescesery .
if they are slightly open ill get a bad clearance any way and adjusting shims would not rectifie this

im unfamiliure with the auto timeing advancer can you tell me what it is where i would find it and roughly how it works im unsure if i have one
 

·
itching to ride
Joined
·
2,238 Posts
How many miles on the bike? A high mileage engine would more likely have some of those issues but I would not rule it out in a low mileage one either depending on how it was taken care of previously. Before I tore into the engine I would check valve clearances since that is easily done once you pull the cover. All you need is a feeler guage. That will give you more ideas as to what could be your problem.
 

·
2storke god 4stroke nub
Joined
·
26 Posts
Discussion Starter · #16 ·
well; it was more then worth going in there!!!!!!!!

i went round takeing all clearances
put fuel in my carb holes and wached with a pen light as my friend cranked to see if fuel culd work its way past the valve i saw nuthing but
when the fuel droped in to the chamber and got compressed i culd see it bubleing around the valves so i kno most of my valves are leaking

then............

when we started to take the covers off the inlet shaft
we found that the bolts on these covers the ones that hold the shaft in
were infact loose

not only that..

but when we tryed to do them up they didnt take just kept turning

turns out sum 1 has been in there allready and didnt do a good job.. obviously overtightened the bolts and destroyed the thread in the head

no wonder it sounded rough from the valves

i hate to think of the posible damage that has been done so....

eather repair it with helicoil n see how it runs

or new head n see how it runs

and if its still playing up re do the valve clearances

and post them here

im thinking more new head as i dont kno the full extent of the damage it has ran with them bolts loose so the shaft might be bent for all i kno

i kno my valves are leaking so to speak and the lack of them bolts wont change that they would need re seating if i keep this head
 

·
2storke god 4stroke nub
Joined
·
26 Posts
Discussion Starter · #17 ·
found a head 40 pounds or about 80 dollors
only one i can find on ebay its buy it now so if i decide i want it i can just buy n pay instantly and it will be on the way

im asking questions about it waiting for responce

problem is tho it comes with valves springs shims buckets all in place there are no shafts if i get it ill be useing my own shafts and mine could be bent

geting it would instantly fix the thread thats gone valves im asking about but as hes not got shafts he wont kno clearances or how well the valves seal

the first person to decide they want it will get it ...

i could also ring partfinder uk they email over 200 uk breakers saying i want this and if the breaker has the part i want they ring me with prices
 

·
Navy Vet Search & Rescue
Joined
·
8,843 Posts
If you decide to buy the other head, make sure the bearing caps come with it. Some sellers will try to sell the head and caps seperately :-? and you need to ones that came with that head from the factory. Never seen a bent shaft and I'm not sure how anyone would bend one with normal use.
 
1 - 20 of 24 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top