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2 bikes = twice as happy
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Discussion Starter #1
Keep getting this strange misfire, flat spot thingy.....

Its intermittent and I can't make it happen deliberately but this is the usual story...

Usually happens going into a decent corner - about fifty or so, feather the throttle while I judge the corner, then as I open up again I get no response, in fact worse, it feels like the engine has cut out. After a second or so it picks up and everything is fine. Strangely has happened a lot more with a pillion on.

Feels like carburation - could be icing in the Carb, or that PAIR thing - which I don't understand.

Suggestions???
 

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xrv750x Pilot
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585 Posts
Hi Austin Do you ride an Early 600 ? .I had a 1989 model and the C.D.I. units under the seat had the wires going upwards to the base of the seat " These were changed on some bikes " to sit sideways as the weight on the seat pushed down on the wires causing the C.D.I. units to fail.One of my C.D.I.s failed this way . Loss of power , missing a beat once every now and then , The bike would start and tickover and rev But when i sat on it the misfire would start. Another thing that happened to me twice in the 78,000 miles that i had the T.A. was the cutout switch on the right handlebar even tho i had never used it failed "water gets into it" and it caused the same problems missfires etc ,Be sure to check your connections on the battery and the lead that goes to either the frame or the back of the starter i cannot remember which as it has been known to rot away and this will cause the same problems . I hope this helps fw750x
 

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xrv750x Pilot
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585 Posts
Hi Austin i have just remembered did you notice if your rev counter stopped working ,It is connected to one of the C.D.I.s .You can swap them round as they are both the same , If the rev counter is not working you can be sure one of the C.D.I.s is not working. Some people on the Transalp forum "DETI,s "carefully took them apart and resoldered all the joints and got them working again. fw750x
 

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2 bikes = twice as happy
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Discussion Starter #4
Hi Austin Do you ride an Early 600 ?
Thanks, FWxxxX [the seven, five and zero keys don't work on me kevboard!!!!] but I ride a 2thousand and 1 Six Fifty.

Problem doesn't feel electrical - but I could be wrong [I often am :oops: but don't tell the wife ]
 

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Golam Rosewater
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1,444 Posts
Sounds just like when I opened the airbox up with too many holes. bike ran too lean.

Check airbox rubber trumpet thingies for leaks ?
 

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:withstupid:

Yup, I'd say check where all hoses fit to the airbox and as wheeliebin said the engine/airbox rubbers.

You serviced it recently i.e. had the airbox off???

Phil
 

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2 bikes = twice as happy
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Discussion Starter #7
Yup, I'd say check where all hoses fit to the airbox and as wheeliebin said the engine/airbox rubbers.

You serviced it recently i.e. had the airbox off???
Didn't think it would long 'til you and Wheeliebin came along, Phil. Thanks.
Not had airbox off since I serviced it 2thousand or so miles ago in about February, but I did fit a KandN air filter then. Mostly runs OK but this is a fairly recent phenomenon. I did finish off the February service this weekend :oops: and replaced the two plugs I couldn't get out back then [also wanted to eliminate plugs as a cause]. Plug Colour etc looked OK, if it was lean plugs would look white and blistered wouldn't they?
Nevertheless sounds like something else to look at next time fairing and tank are off or sooner if it gets worse. [Don't ya just hate the fairing/tank removal job :twisted: ]
 

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[Don't ya just hate the fairing/tank removal job ]

YES :evil:

When did this start, after the service? or after the K&N?

Whats consumption, has it altered???

Just wondering if your bike was running leaner than the rest of ours (hence good fuel economy), the K&N has just pushed it too far (too lean).... Hence the troubles?!?

Might be worth popping the stock filter back in. PITA, I know (can be done with fairing in place)

Since drilling a few holes in the airbox my bike returned 56mpg going to Lakes. A first.

Phil
 

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Yup feel's good, can't say wether any more power, but got good delivery, haven't brimmed it again yet. might have been a fluke :? Gauge not looking too good this time. Mind I was sat at 95 most of the way home on Sunday :wink:

Redlined in top happily enough (slight uphill, headwind and with camping gear) 8) .

Not too keen on airbox noise but can live with it if it gives extra 8mpg.

Phil
 

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2 bikes = twice as happy
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Discussion Starter #11
When did this start, after the service? or after the K&N?
After both :? Noticed it first about 3-4 weeks ago with son on he back. Most mileage is a trip up and down M6 to work and it never happens at steadv speeds.

Whats consumption, has it altered???
Not reallv, m6 run still doing high fifties or sixty mpg[22O+ miles to a tank {seventeen ish litres}]. On weekend blasts I reckon I am down five mpg. :(

Just wondering if your bike was running leaner than the rest of ours (hence good fuel economy), the K&N has just pushed it too far (too lean).... Hence the troubles?!?

Might be worth popping the stock filter back in. PITA, I know (can be done with fairing in place)
Prettv sure I chucked the old filter out. I was thinking about what u and wheeliebin suggested, and I had alreadv noticed a full on induction roar when I give it fullish throttle, so could be a leak somewhere. Will investigate.

Since drilling a few holes in the airbox my bike returned 56mpg going to Lakes. A first. When did this start, after the service? or after the K&N?
:hello1: Its the steadv runs that make the difference. :thumbright:
 

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51 Buell X1 & 89 Tenere
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292 Posts
Austin said:
When did this start, after the service? or after the K&N?
After both :? Noticed it first about 3-4 weeks ago with son on he back. Most mileage is a trip up and down M6 to work and it never happens at steadv speeds.

Whats consumption, has it altered???
Not reallv, m6 run still doing high fifties or sixty mpg[22O+ miles to a tank {seventeen ish litres}]. On weekend blasts I reckon I am down five mpg. :(

Just wondering if your bike was running leaner than the rest of ours (hence good fuel economy), the K&N has just pushed it too far (too lean).... Hence the troubles?!?

Might be worth popping the stock filter back in. PITA, I know (can be done with fairing in place)
Prettv sure I chucked the old filter out. I was thinking about what u and wheeliebin suggested, and I had alreadv noticed a full on induction roar when I give it fullish throttle, so could be a leak somewhere. Will investigate.

Since drilling a few holes in the airbox my bike returned 56mpg going to Lakes. A first. When did this start, after the service? or after the K&N?
:hello1: Its the steadv runs that make the difference. :thumbright:
220 miles to a tank! I think mine must be playing up, I only get 150 tops! Admittedly round town riding, but mine smells a bit rich, and I get the odd backfire at 3kish but not serious. I think I will check my hoses out as well.

I have heard if you squirt easy start in the air filter of turbo cars , the revs will rise if there is a leak , might be the same for bikes! :wink:
 

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Last of the Minoans
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I wasn't going to post on this topic in the hope that you might find the cause in the meantime, because I have the same problem.....

I've had the problem for quite a while now, but it's getting worse. It's now starting to happen at lower speeds (30-40-ish). I figured it might be the dreaded sticking choke at first, but I had the chokes out at the weekend and all is fine there. Anyway, I never use the choke in case this problem manifests! ATs can get a similar problem with lean running when the air box isn't on properly - Yen recommends not tightening the clamps to avoid this, and I've followed that advice. I have no idea how likely this is on a 650 TA. However, in my case the intermittency and the fact that there is no popping and banging on the overrun (which you get with an air leak) certainly suggests it isn't lean running. Do you get the popping?

In my case I suspect the problem is in fact electrical. Yesterday the tickover was rough - just like the poor balance you get if you dislodge the Scottoiler vacuum feed, but the problem had cleared up by the end of the day. Now, I had a similar problem a while ago on a 600 TA. In that case it got worse on damp days - a dead give away. Eventually I tracked it down to the LT lead on the rear coil - it had been rubbing against the frame and was shorting against it. Easy to cure with insulating tape. I suspect my current problem is something similar because it has to be something that affects the the whole cylinder rather than just one plug. Try taking a plug lead off and running the engine - there isn't much difference in running. If your problem is something similar, check the front coil - it can catch a lot of road crud, especially if you've ridden it through the winter. Yen regularly has problems with corrosion of the LT spade connector caused by salt. If an LT problem is what's affecting yours and mine, I suspect what's happening is that as we close the throttle for the corner the revs drop and the feed to the LT is so weak (either through corrosion or shorting) that the spark becomes intermittent and weak; when the throttle is opened again the cylinder briefly fails to fire.

I'll be having a good hunt around at the weekend. Anyway, something to consider....

Good luck in your search!

Stig
 

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2 bikes = twice as happy
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Discussion Starter #14
Lord Stig said:
I wasn't going to post on this topic in the hope that you might find the cause in the meantime, because I have the same problem.....

I've had the problem for quite a while now, but it's getting worse. It's now starting to happen at lower speeds (30-40-ish). I figured it might be the dreaded sticking choke at first, but I had the chokes out at the weekend and all is fine there. Anyway, I never use the choke in case this problem manifests! ATs can get a similar problem with lean running when the air box isn't on properly - Yen recommends not tightening the clamps to avoid this, and I've followed that advice. I have no idea how likely this is on a 650 TA. However, in my case the intermittency and the fact that there is no popping and banging on the overrun (which you get with an air leak) certainly suggests it isn't lean running. Do you get the popping?

In my case I suspect the problem is in fact electrical. Yesterday the tickover was rough - just like the poor balance you get if you dislodge the Scottoiler vacuum feed, but the problem had cleared up by the end of the day. Now, I had a similar problem a while ago on a 600 TA. In that case it got worse on damp days - a dead give away. Eventually I tracked it down to the LT lead on the rear coil - it had been rubbing against the frame and was shorting against it. Easy to cure with insulating tape. I suspect my current problem is something similar because it has to be something that affects the the whole cylinder rather than just one plug. Try taking a plug lead off and running the engine - there isn't much difference in running. If your problem is something similar, check the front coil - it can catch a lot of road crud, especially if you've ridden it through the winter. Yen regularly has problems with corrosion of the LT spade connector caused by salt. If an LT problem is what's affecting yours and mine, I suspect what's happening is that as we close the throttle for the corner the revs drop and the feed to the LT is so weak (either through corrosion or shorting) that the spark becomes intermittent and weak; when the throttle is opened again the cylinder briefly fails to fire.

I'll be having a good hunt around at the weekend. Anyway, something to consider....

Good luck in your search!

Stig
Do I get popping ? No, not at all. My experience would suggest popping in exhaust would be caused by leaks at or near exhaust manifold. Leaks on the inlet side will cause lean running and if bad, spitting back into the Carbs - had a Honda 2fifty once without an airbox that regularl used to spit the carbs of the inlet stubs :?

Bike starts without choke most times, so I am thinking less about lean running. My problem onl happens after a second or two on a neutral throttle as I open up again. So something happening that causes either weak sparks or fuel shortage - still think icing could be it (will have a think about weather conditions as well].

Whatever, will have fairing and tank off again :x this weekend and have a poke about the airbox and coils.
 

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Last of the Minoans
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Yes, it's true that popping is what you get with a leak at the manifold, but I've had it often when my Scottoiler vacuum works loose - it shouldn't cause it but it does.

Mine's still doing it, but it occurred to me last night that it rarely happens on the way home, normally only early in the morning. I was wondering about blocked fuel tank breathers. I fill up when I get home, so the air gap is smaller. Dunno. Another possibility closer to what you were originally thinking is a malfunctioning throttle sensor not advancing the timing.

My thoughts are a bit dark this morning - I managed to isolate the noise mine's been making, and I don't think it's related to the cutting out problem. It's coming from the top end right at the nearside of the front cylinder. Doesn't sound like a valve-like sound, more of a knock. I'm thinking cam end float or possibly cam chain (not a rattle though). Hummpphhh.

Stig
 

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Austin, I'd keep tracking a leak at the inlet side/lean running - especially as it's just a fairly recent event, lots of fiddly pipes around the airbox, one could have easily been dislodged.

The bike is fitted with carb heaters, so shouldn't be a problem, TPS, again, probably clutching at straws, if the bike otherwise runs fine.

Sure while youv'e got the tank off pull all the connectors apart and vaseline them.

Stig, has this knock started since you balanced the carbs???
Poor carb synch can make a knocky type noise from the top end as can poorly adjusted pilot screws.
Maybe worth rechecking the carb synch?

Just a few thoughts, maybe of help, maybe not!

Phil
 

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2 bikes = twice as happy
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Discussion Starter #17
OK, I have had a look and a poke about, nothing obvious - not sure if that is good or bad. I can't replicate the problem at all now. In fact since posting this, it hasn't happened. Been out for a good blast today round Bowland and no amount of throttle wringing, open/shut, partially open, etc etc caused any sort of misfire or hesitation. So, one of those transient problems and gone away until it happens again.

More news though - been upgrading the lights - fitted some dinky little fog lights to the crash bars and upgraded the headlight bulb with one of those 6O per cent brighter bulbs. Driving at night is loads better now - just in time for summer :?

Will post some piccies when I get round to a. taking photos, and b. learning how to shrink them and, c. working out how to upload them!
 
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