What the f!@?! is wrong with my bike!? (Honda GB)

[sammcj]

is the choke cable mybe seized inside the outer ??we just had a problem with a seized hot start lever that had the same symptoms it also looked very much like your choke cable .. have you tried undoing the plastic nut and trying to free the cable ??

Good plan, pretty sure KG replaced it with a new one during the bore out to 600 due to them melting it against the engine fins

How tight is the end of the cable outter (the metal part) meant to sit in the carb? i.e. should it take much effort to pull it out exposing the cable going into the plastic nut?

[Henk]

Not sure if this will help, haven't seen the video but, had a TTR600 a few years back that started missing and backfiring like a bastard. Did this at any revs, turned out the wiring where it came out of the CDI had worn through the insulation and vibration would run it into the frame and cause the miss. With everything you've already done I'd be having a look at the leckies to see if you don't have an intermittent short.

[laserracer]

Good plan, pretty sure KG replaced it with a new one during the bore out to 600 due to them melting it against the engine fins

How tight is the end of the cable outter (the metal part) meant to sit in the carb? i.e. should it take much effort to pull it out exposing the cable going into the plastic nut?

ours was really loose because the piston/plunger was stuck in its housing in the carb and the spring wasnt doing its job properly,when fixed you could still pull it out of the nut but it was under tension

[sammcj]

OK, I took the tank, headlight, battery all off and checked over the wiring.

-I noticed the plastic connector that plugs into the headlight bulb is quite melted, I'm wondering if it's arking across the points?... this might be debunked by the fact it still has the same issue when the headlight is turned off.

-After checking the fuse box I found one of the 10A fuses to be blown... but it wasn't for the headlight, the original gb service manual doesn't list what each fuse connects to, the fuse in question is on the far right hand side.

-I pushed the choke cable firmly into the carb and rode into town, ran fine when the bike was cold, idled at 1200rpm at the lights without choke... got about 4 - 5KM away from my house and it started stall at low rpm again, by the time I filled up with gass and stated riding home it was running like a real dog in the lows, coming up to lights at <300RPM she shakes around while you hear her spitting out air.

[vagrant]

It does sound like a choke issue.
My fireblade started running very rough and missing at idle after I had loaned it to a friend. I have never needed to use the choke, and I know the cable is stuffed. He tried to used it, got it part open and the cable broke, so he pushed the end back in, but it did not close the choke properly, hence over rich running at low throttle openings. He just wound the idle screw down a bit to cover it. Also forgot to mention the broken cable.

[jellywrestler]

maybe the coil or cdi is breaking down when hot???

[laserracer]

have you checked the petrol cap vent hole it might be blocked when it starts to play up try taking off the petrol cap and see if it makes a difference

[roadracingoldfart]

OK So I've made a few post on KB about some issues I've had with my 1986 Honda GB before, mainly to do with loss of power and bad idle / 'popping and stopping'.

So far, I've had 3 people look over it, mainly KG Motorcycles here in CHCH, no one can find the fault!

It randomly pop's and stops, you hear air making a popping noise somewhere and the RPM drops about 1000, this only occurs on idle however I do have a feeling there is some power missing from the engine.

It was a 500cc and was bored out to 600cc, it did pop and stop before the bore but it is worse now, probably due to the extra bore size.

KG has replaced:
-The carb
-The Ignition / CDI
-The generator
-Checked over wiring (but he's probably not very good at that!)
-Replaced muffler with a more free flowing one
-Valve clearances are good (thanks to help from T.W.R.!)
-Disconnected battery and checked charging rate
-Replaced coil under clutch cover (can't remember the name of it)
-Pretty sure there are no air leaks coming into carb
-Carb has been fully disassembled twice and checked over.
-Carb re-jetted
-Spark plug and gap is fine
-no airbox obstruction
-It's noticeably worse when it's hot.
-I have seen the indicators go to fast as if there was a blown bulb at times.

The head was leaking a bit of oil around the seal and KG put a new gasket on it yesterday, also did an oil change - after this it's running much worse today than it ever has.
KG motorcycles has spent countless hours trying to fix this and now doesn't want to see the bike again and to be honest I've lost all faith with them!


I've uploaded a video to youtube of it doing it REALLY badly (After the CHCH ACC ride today)

If you're the one that has the right solution for it I'll buy you some beers!

Here is the video (youtube is processing it now so it might take a moment to appear).

http://www.youtube.com/watch?v=Il84EYkAT5E

Check the decompression valve on the r/h side of the head . If you hear a popping sound it could be a case of it not seating and that will give you a compression leak out the pipe.
The semi melted plug bit is just common , check the regulator rectifier for values.
The GB range of bikes are very very fussy on thier tappit settings so even though you say they are set , are they set properly ?
When they first came out i and all Honda techs used to pull large amounts of hair out trying to get them sussed after the first service , it all came down to valves and air flow / leak issues.

Cheers Paul.

[sammcj]

OK, thank you all very much for your input, much appreciated!

Are the tappet settings the same as valve clearances? (Sorry I'm pretty new to this)

Tonight / Tomorrow Night I'll Be Checking The Following:

-Decompression Valve / Lever

-Valve Clearances (again)

-Petrol Tank Vent

-Choke cable possibly not working correctly (I found from the manual the needle is supposed to poke out 10-20mm)

[MSTRS:Me]

Check the decompression valve on the r/h side of the head .

This would be a priority check for me too.
The problems you have seem to be 'hot' issues, which strongly suggest expansion problems with area/s that that have critical tolerances.
I doubt the melted h/light plug is involved - that is a separate issue.
Also not likely to be a coil...they fail under load, not at idle.

[laserracer]

So how did you get on ??????

[sammcj]

So how did you get on ??????

ugh i've been bogged down a bit sick, spoke to kg asking if he'd fiddled with anything that could have made it worse, he said it could be the o-ring coming into the carb, im going to pop by and have a look at it with him tomorrow (he's not charging as it may be his fault)

I'll let you know asap!

[CookMySock]

I actually wonder if its running real real lean - that will make it pop and backfire when ridden anything but very lightly. Is the exhaust sooty and black? Is there any blueing on the exhaust near the cylinder? Try starting it from dead cold (first start of the day) with no choke - if its too lean it will be fooken hard to get going.

Steve

[sammcj]

I actually wonder if its running real real lean - that will make it pop and backfire when ridden anything but very lightly. Is the exhaust sooty and black? Is there any blueing on the exhaust near the cylinder? Try starting it from dead cold (first start of the day) with no choke - if its too lean it will be fooken hard to get going.

Steve

Exhaust is quite sooty & black.
Backfires on revving down (i.e. coming up to lights / stop)
There is no way you'd get it started from cold without the choke.

[AllanB]

Check the plug and see what it looks like - it will tell you if it is lean or rich. Also make sure they have the correct plug in there - it may be the wrong heat setting. Lean will pop on decel and if it is mega rich (I doubt as you probably not need choke then) maybe it's unburnt fuel igniting.

Cable - even if it is new it may be obstructed somewhere under the tank when you turn the bars and thus gets pulled slightly open. If in doubt remove it and reroute it on the outside where it is 100% free of any obstructions (use a bit of duct tape to hold it temporarily in place against the tank or frame if necessary) - does this make a difference?

Carb rubber - the rubber between the head and carb and or carb and airbox - they may have holes and be leaking. A check apparently is to spray them with WD40, run the bike and look for bubbles or holes in the oil coating.

Alternatively buy a Suzuki - at least you'll expect problems then .....