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YB 8 not running
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tenchu2x



Joined: 09 Sep 2015
Posts: 107

PostPosted: Sat Jun 29, 2019 10:48 am    Post subject: YB 8 not running Reply with quote

Hi guys,

i am a new owner of a YB8 Standard with Mikuni carbs and i have Problem swith it Right from the Start.
the first 2 times i rode ist i notice that bekow 5k it was sturttering in a way and not running properly . above was good. after the 3rd ride when i put the bike on a stand, it started dropping all the fuel.

i checked and i saw that one of the fuel pipes outside of the tank was broken,

replaced it.

now i just rode it again. it started immideatley running good and first 2-5 minutes rode well, then it started again stuttering. stuttering went worse. bike went out driving. with a lot of luck i managed to start it again. but only with a lot of idling. i had to rev it at the lights else it would go out. it was not running normaly, sounding strange and the "not burnt fuel"-sounds coming from the exhaust. was not possible to get higer revs, it did not respond good to the throttle. all in all was not nomal. maybe only ran on 3 or 2 cylinders ?

ok i managed to get home somehow. checked again under the tank but i do not see any other broken fuel hoses, they all seem finde and it is not leaking fuel.

what is going on?

the fuel filter out of the tank has the writing " FRAM 04164" on it, which i cant find in the net. i am thinking of repalcing it, but with what?

next iguess what be the fuel pump.. which one i can use?

any other tipps what i should try next?

Cheers Robert
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Sat Jun 29, 2019 12:11 pm    Post subject: YB8 Reply with quote

Robert, the key issue with a YB8 is the fuel & crankcase breather plumbing under the tank. Unless it is right, there is a good chance that once you have dropped the tank in on top of it and can no longer see what’s going on, that a bend in the hose will become a kink once the motor has heated up the rubber, leading to starvation. If you have replaced some of your plumbing, there is a good chance that it is now less than optimally configured. Happy to send you a photo of my configuration if you pm me your e-mail. The next issue is whether the carbs need a clean and new O rings and setting up.
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Sat Jun 29, 2019 12:18 pm    Post subject: YB8 Reply with quote

Should have asked, is the pump cycling for 5 seconds when you turn on the ignition? The original pumps are no longer available, but Tourmax sells the electrics to allow you to repair your old one. Failing that, there are identical aftermarket pumps for FZR 1000 available from the US. A K&N air filter is available.
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tenchu2x



Joined: 09 Sep 2015
Posts: 107

PostPosted: Sat Jun 29, 2019 8:42 pm    Post subject: Reply with quote

Hi Johnny,

thx for comming back.

- yes, pump is ticking whn turning the key on. but i think that does ont mean its ok necessarily

- can you tell me where to get an fitting aftermarket pump? or what it is called?

- yes, pls send me your hoses configuration of underneath the tank my email adress is haeusler.robert(at)gmail.com

i noticed that also the hose of the crenankcase breather here it goes into the airbox is loose. but that should not cause the problem, right?

- i noticed also on the airbox another connection on the other side, which is not used, what is this?

- i made some pics of man under tank setup.

https://imgur.com/gallery/8eg1Ekm


- oh, pls send me the name and maybe shop where i can by fuel filter and fuel pump, i think these are the next ones to try plus the setup maybe.

i tend to think that the reason why it starts right away when it is called because then the carburetors are full of gas after turning on the key several times and the pump getting fuel in there.
then when riding a few minutes all gets warmer and something happens. either the pump is not wotking Right , the filter is closed, or something is obstructed so not enough fuel gets there. then it eventually went out. when i managed to get it running again a little , i think only the cylinders ran , where there was still a little fuel left, the others did not. thats my theory. but ti could also be the carburetors. but then: would not the problem be there right from the start?

Thx dn cheers Robert
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Sun Jun 30, 2019 9:29 am    Post subject: YB8 Reply with quote

e-mail sent Robert.
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tenchu2x



Joined: 09 Sep 2015
Posts: 107

PostPosted: Sat Jul 20, 2019 4:28 pm    Post subject: Reply with quote

what the F...

i think i found the error, i rerouted all the fuel hoses but still had the Problem...machine stuttering and going out....then i noticed that the fuel taps are leaking but i could repair that.

anyway the Problem still existed…

then i think i got the lucky Moment , with the last time pushing in the tank i detroyes the power cable for the fuel pump accidently... well i thought...no biggie, i repaired the cable and then i got a Eureka Moment:

when i switched on the ignition i immidiedatly noticed that the fuel pump was different than before...i meant yes the fuel pump was Cycling before but... different...not so fast and not so regular. now it is super fast and Always 5 seconds whan i turn on the iginiton key. before it was only Cycling on the firest time. when i switched off and on again it was not so Long. i thought it was normal, since the carburetors were fuel then.

i assume that before the cable already has bad contact. the devilish thing is that the fuel pump still worked with that...so i ruled it out as an error source...with the cable going completley defective now i got lucky...i would never found that error.

still have to test Ride it though...Keep fingers crossed… i am not sure ist over yet...
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tenchu2x



Joined: 09 Sep 2015
Posts: 107

PostPosted: Mon Jul 22, 2019 6:35 pm    Post subject: Reply with quote

Hmm seems not over yet ...

Stupid question : when the carburetors are full , will the fuel pump tick anyway at starting for 5 seconds ? Or not ?
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rOLLI



Joined: 10 Jan 2019
Posts: 97
Location: germany

PostPosted: Tue Jul 23, 2019 8:22 am    Post subject: Reply with quote

Hi Robert,

when my carburettors (YB8 ) are full, then the pump does not work anymore, even when I switch ignition on and off. So this is correct.

kind regards from south germany Roland

I seems, you are also active in MV Forum ?
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tenchu2x



Joined: 09 Sep 2015
Posts: 107

PostPosted: Tue Jul 23, 2019 2:55 pm    Post subject: Reply with quote

thx,

i just sent you a PN too.

i still change the pump now, since i have to rule this out,

if i can rule out pump and fuel hoses, then it must be carbs.
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YBista



Joined: 23 Jul 2019
Posts: 11
Location: UK

PostPosted: Tue Jul 30, 2019 2:04 pm    Post subject: Reply with quote

Hi,
I'm probably too late ,but before you change the fuel pump I suggest you test it (at least in static mode).If successful it does not guarantee the fuel pump is OK but it is a very good indicator..
The point of this test is to focus on the arrangements with all the components in their fitted position, ie ensure that the fuel tank and pipes are positioned correctly,just as if you are riding the bike.
In order to test it you need to disconnect the petrol pipe from the carbs (ie after the fuel filter and pump)and then connect a new pipe to this disconnected pipe so that you can redirect the pumped fuel into a measuring vessel. Once you've made all the connections ,and confirmed no leaks etc , then you can start the test: switch on the ignition but with the RUN SWITCH in the OFF position. Now start the clock and switch the RUN SWITCH on.Do not attempt to start the engine, as you just want to measure the fuel flow.The fuel pump will stop every 8-10 seconds , as a safety feature ,so you need to switch the RUN SWITCH off and on swiftly every time the fuel pump stops , just to get a continuous reading . Ideally the flow rate is about 1 pint every 1 minute.You may find the flow rate is a bit better when the tank is at least half full. This test can ID faulty fuel pump,filter,fuel taps ,pipes or pipe routes.As has already been mentioned the fuel pipe route is CRITICAL ,so if the test fails I suggest you start by centring your attention on this area. You can experiment with different arrangements and then retest accordingly.
Obviously you are dealing with a highly flammable liquid so follow all necessary safety precautions.
Hope this helps.
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YBista



Joined: 23 Jul 2019
Posts: 11
Location: UK

PostPosted: Tue Jul 30, 2019 2:04 pm    Post subject: Reply with quote

Hi,
I'm probably too late ,but before you change the fuel pump I suggest you test it (at least in static mode).If successful it does not guarantee the fuel pump is OK but it is a very good indicator..
The point of this test is to focus on the arrangements with all the components in their fitted position, ie ensure that the fuel tank and pipes are positioned correctly,just as if you are riding the bike.
In order to test it you need to disconnect the petrol pipe from the carbs (ie after the fuel filter and pump)and then connect a new pipe to this disconnected pipe so that you can redirect the pumped fuel into a measuring vessel. Once you've made all the connections ,and confirmed no leaks etc , then you can start the test: switch on the ignition but with the RUN SWITCH in the OFF position. Now start the clock and switch the RUN SWITCH on.Do not attempt to start the engine, as you just want to measure the fuel flow.The fuel pump will stop every 8-10 seconds , as a safety feature ,so you need to switch the RUN SWITCH off and on swiftly every time the fuel pump stops , just to get a continuous reading . Ideally the flow rate is about 1 pint every 1 minute.You may find the flow rate is a bit better when the tank is at least half full. This test can ID faulty fuel pump,filter,fuel taps ,pipes or pipe routes.As has already been mentioned the fuel pipe route is CRITICAL ,so if the test fails I suggest you start by centring your attention on this area. You can experiment with different arrangements and then retest accordingly.
Obviously you are dealing with a highly flammable liquid so follow all necessary safety precautions.
Hope this helps.
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tenchu2x



Joined: 09 Sep 2015
Posts: 107

PostPosted: Sat Aug 03, 2019 4:32 pm    Post subject: Reply with quote

ok, i have some news:

I changed:

- the fuel pump
- the fuel pump relais
some routing


Good news:

The Bike is running!

Bad News: i have the problem with riding with revs below 4k.

ok, how, does the bike behave:

- Idling while standing: superfine, no problems. it does not go out. it is running forever like this. no issues

- reving while idling and standing: no probems, i can rev it up without any stuttering etc.

BUT: when trying to get the bike moving, i have to play a lot with the clutch to get it going with rather high revs, because else it is not really moving and also eventually goes out.
Once the bike is moving and the revs are reaching 4000 everything is superfine. i rode the bike now 50kilometres and cranked it up quite heavily on the motorway. as long as you keep it up above 4000 rpm all is fine. it accelartes smooth and fine no matter what gear, also i can give it fullgas and no stuttering whatsover.

BUT: if the bike is below 4000rpm, it does not move forward, when i apply more throttle more throttle in this situation, eventually it will go up to 4000 and then it is no prob. but it is really a hassle starting to move the bike from standing. below 4k it does not respond th throttle. i pull the throttle and nothing or nearly nothing happens. it is strange that reving the bike while in idle does work on the other hand without problems. but whith the bike moving i get the problem, only below 4k.

as you know i am not a technican but i try to think logically. the bike has carbs.

I THINK: if the bile still would have a problem with the fuel hoses or routing or not enough fuel getting through, i think it would behave differently. logically i would have more problems when going faster, going fullgas and reving it up. but its the other way round. i only have the prob when in low revs.

Also it has carbs and tehre is a little amount of fuel in it. even if there would come nothing to the hoses but with full carbs it would run perfectly until the carbs run out. but the carbs do not run out obvously.

if i would still have fuel starvation, i think the bile would run fine as long as going slow, but when going fast and high revs it would have problems because then it would need more fuel and it does not get it.

is my thought correct, or can it still be the fuel routing?

i want to rule that out completely.

if i can rule it out, then i guess i need to clean and setup the carbs next thing. but then i dont want to do this, before i can rule out the fuel situation before.

Thx a lot guys
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Bud977



Joined: 03 Mar 2013
Posts: 525
Location: Sydney

PostPosted: Sun Aug 04, 2019 12:33 am    Post subject: Reply with quote

The pilot jets are blocked. Pull the carbs out and give the pilots a clean using fine wire like a guitar string.
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firststrike



Joined: 23 May 2010
Posts: 38
Location: swansea

PostPosted: Sun Aug 04, 2019 9:44 pm    Post subject: Reply with quote

Agree with Bud, Carbs need a thorough cleaning. Be careful with wire cleaners that you don't break one in the jet.
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Sun Aug 04, 2019 11:10 pm    Post subject: Reply with quote

I agree with both....which are the same comments.....its not low fuel its pilot jets for low speed/revs running...fine when idling because there is ZERO load on the engine so its just ticking over....load is the effort in moving the bike forward when youre on it and the mass of the bike...thats when issues start...after 4thou....pilot lets not needed so runs fine...….I presume you have new fuel of high octane in it?......Have you tried running carb cleaner through the carbs or an additive in the fuel that can clean carbs.....as I understand your reluctance to pull and strip the carbs down....so want to try a quick fix of simply adding a fuel additive that MIGHT solve this problem just by riding the bike....Any suggestions lads on a fuel additive carb cleaner that folk have used and it worked?
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