660 not liking the choke

[old_fogey]

My 91 seemed to do what yours is doing.

It all ran fine when I picked up the bike, then I ran cleaner through a fuel tank a month later. That's when the problems all started.
Sputtery when it was cold (choke helped but it was hit & miss). Once it got warmed up, it ran fine (but a miss here or there), but if I turned it off, it was taking forever to restart it until I let it cool down.
I noticed a smell of fuel as well from time to time as if it were leaking from a cracked hose or what not.

So this winter, I ripped the carbs off and stripped them down to clean them. I ran them singularly to the fuel pump to test if the floats were sticking. Once I let them fill up, then let them sit, 2 of the 4 would drip fuel into the intake. So from there, I knew the issue and got it all back together. I still need to tweek the sync- setup a bit as I first did them when it was in the 60s out

I was told to replace the "choke" lever as well as they tend to fray and not react smoothly. Mine is fine, but I believe my son's 94 has this issue as the RPMs do not react smoothly and tend to jump around when adjusting the lever.

Tim

[ranmafan]

So this winter, I ripped the carbs off and stripped them down to clean them. I ran them singularly to the fuel pump to test if the floats were sticking. Once I let them fill up, then let them sit, 2 of the 4 would drip fuel into the intake. So from there, I knew the issue and got it all back together. I still need to tweek the sync- setup a bit as I first did them when it was in the 60s out

Mm, that sounds entirely different, actually... I've cleaned/touched up the tank (H2PO4), replaced fuel filter (transparent NAPA piece), rebuilt the (YZF) carbs (new everything except emulsion tubes, even the valve seats - K&L and FP kits), and replaced the plugs right after the topend rebuild (no Autolites sold around here!). If I had another bike to ride, tearing everything right down to bare frame would have been a much better option...

Now that I have 520 chain/sprockets and new tires on, I can't even complain about low-speed lurching anymore... just a little groggy waking up in the morning, that's all

At any rate, I'll be dropping the rad and checking the #2 plug (and compression, while I'm at it) later today. The Archives make it seem like #2 fouling once in a while is not uncommon... we'll see.

[CJD]

I did check/clean the rest of the connections, they all should fine (southern Alberta is a pretty dry place, anyway...). I'm now getting a voltage drop of about 0.8V between the battery and coil inputs with the key on. I've no idea how TCI outputs look like, but that sounds about right for, say, one silicon p-n junction...

You have a 20 year old bike, oxidization takes it's toll in any climate, You need to find the source of the voltage drop, look at the wiring diagram I posted earlier, it shows the harness/loom connection blocks. http://imageshack.us/photo/my-images/21 ... gram1.jpg/

Any of those connections leading to the coils and/or the kill switch could have oxidization including the main fuse and ignition fuse, Yes spade fuses deteriorate/oxidize over time. Pull the main fuse and ignition fuse, clean the spades on both fuses with sand paper, even if the fuse looks clean.

Then there's the single connection block between the battery and the VR, its white in color located under the seat close to the TCI. Clean that also, basically if it looks clean, clean it anyways.

Have you checked the voltage delivered to the TCI (the red/black wire) fed VIA the kill switch, it's probably lower than the voltage delivered to the coils, taking into account it's fed by the kill switch.

Unlike before, it fires right up with its own battery and choke on (everything else is about the same). Once it's warm, however:

(choke on all the way)
- goes up to ~3k RPM
- a moment later, slowly starts to drop back down to ~2k
- at the same time, cylinder #2 exhaust temperature starts dropping like a rock, from ~220C to below 100C, while the rest stay around 180C
(choke off, all cylinders idle at around 220-240C)

I'm guessing #2 plug is not gapped correctly....

Errrr the choke is well.... to enable the engine to start when cold, and should be shut off when the engine is warm, any engine whilst warm don't like the choke. Are you saying

"Once it's warm, however: (choke on all the way - goes up to ~3k RPM - a moment later, slowly starts to drop back down to ~2k"?

If so that's normal when the engine has warmed up, well not really. When the choke is applied to a warm engine, the engine floods, struggles to run and prolly will cut out.

[ranmafan]

Then there's the single connection block between the battery and the VR, its white in color located under the seat close to the TCI. Clean that also, basically if it looks clean, clean it anyways.

Yep, I'm pretty sure I've cleaned all contacts that could be reached (including main relay, fuses, etc.)

The biggest drop is somewhere around the ignition switch (~0.6V out of 0.8V). Given that it has ~7A flowing through it, that's still only 0.08 Ohm - not that bad, considering there's a few meters of wiring in between. I'm not really convinced there's a problem here, but I'd appreciate if someone could do some measurements on a well-running bike...

Have you checked the voltage delivered to the TCI (the red/black wire) fed VIA the kill switch, it's probably lower than the voltage delivered to the coils, taking into account it's fed by the kill switch.

Haven't written it down, but IIRC it's almost the same - I'd expect very little current running through it.

If so that's normal when the engine has warmed up, well not really. When the choke is applied to a warm engine, the engine floods, struggles to run and prolly will cut out.

Well, I'd expect it to stay at high idle for a little while before starting to foul plugs or trying to flood, at any temperature. At any rate, my idea of "normal" is starting readily (cold) with choke (enrichener) on, then going into high idle at ~3k once it starts to warm up - not asking me to play with the throttle at all once it fires up. What's happening is pretty much the opposite...

By the way, the plugs all look fine (grayish-brown, almost no black, perfect insulator colour). I've tried setting the gap towards the upper end of the spec (0.032") - perhaps the 660 happens to need a "fatter" spark, or my gauge just sucks, and it's actually been set too low before... we'll see tomorrow.

[reelrazor]

I'm thinking higher displacement=better vacuum signal.

Better vacuum signal means enrichment not as necessary on startup

Solution? Live with it, or decrease the starter jet size, and possibly the pilots.

[ranmafan]

I'm thinking higher displacement=better vacuum signal.

Better vacuum signal means enrichment not as necessary on startup

Problem is, it IS still very necessary on cold startup (gotta take another video of that...) Changing pilots or playing with IMS had no noticeable effect.

Tried bigger spark gap (0.032") - doesn't even fire, and plugs are a bit wet. Back to 0.028", same deal with #2. Set IMS to 0.5 turns out, just in case, and left it to cool down overnight....

So it's likely something electrical, and possibly limited to #2 cylinder. Coil and plug cap resistance is within spec (~12 and 9 kOhm, respectively), and the plug itself looks fine. Battery itself is also more or less ruled out.

The one thing I haven't tried yet is exchanging the plug caps between cylinders. Anything else I'm missing? Time for a Ford Escort coil mod, maybe?

[DonTZ125]

Can't remember - have you tried trimming the spark lead, then re-attaching the cap? There've been a few people for whom that's worked wonders.

[ranmafan]

Can't remember - have you tried trimming the spark lead, then re-attaching the cap? There've been a few people for whom that's worked wonders.

Yes, did that. Removed about 0.5" off each wire (all the joints were looking clean and solid, and I was worried I might run out of wire with #4). No effect on resistance, so they were probably fine.

[CJD]

Ok please report what you have done, it's a little frustrating when suggestions are thrown at you, then you discount them and say "already done that" blahah.

Have you yet taken a reading of the coil inputs er.... the red white wires whist the engine is cranking I.E. start button pressed? if so please tell.

Like i said earlier less than 10V delivered to the coils when cranking = a very weak spark, & prolly the reason no fire when you gapped the plugs to 0.032"

Tried bigger spark gap (0.032") - doesn't even fire, and plugs are a bit wet. Back to 0.028", same deal with #2. Set IMS to 0.5 turns out, just in case, and left it to cool down overnight....

So it's likely something electrical, and possibly limited to #2 cylinder. Coil and plug cap resistance is within spec (~12 and 9 kOhm, respectively), and the plug itself looks fine. Battery itself is also more or less ruled out.

The one thing I haven't tried yet is exchanging the plug caps between cylinders. Anything else I'm missing? Time for a Ford Escort coil mod, maybe?

The choke/enrichment is well.... for cold start purpose only, sorry but IMO only a retard would apply the choke when the engine is warm

[ranmafan]

Ok please report what you have done, it's a little frustrating when suggestions are thrown at you, then you discount them and say "already done that" blahah.

Have you yet taken a reading of the coil inputs er.... the red white wires whist the engine is cranking I.E. start button pressed? if so please tell.

Sorry, lemme try summarizing it this way:

Bike:
- 1991 FZR 600 (bottom end, frame)
- some 1997+ YZF600R carbs and head ("660 mod")

Notable symptoms:
- hard to start when cold
- cuts out (floods) if choke isn't promptly closed a few seconds after starting (*before* warming up)
- #2 cylinder floods easily with choke on, any temp (rapid temp drop at exhaust header, RPM decrease)
- starts/runs perfectly once warmed up (choke off, of course)

Already done/tried:

Intake/fuel:
- jetted the carbs (feels pretty good throughout the whole range)
- cleaned/rebuilt the carbs
- synced the carbs (bench, then adjusted a little by ear/IR thermometer)
- checked the choke plungers/cable
- checked for air leaks (reasonably sure there aren't any)
- tried different pilot jet sizes/IMS settings (very little effect)
- cleaned (thoroughly) the tank
- changed fuel filter

Electrical:
- YZF600 VR mod (long time ago)
- checked/cleaned all contacts
- checked primary/secondary coil winding resistance
- checked plug cap resistance
- trimmed plug wires
- checked spark plugs for wear/fouling (looks better than my last set)
- set the gap to ~0.032" - no fire at all (okay, it might have been a tad more than 0.032"...)
- set the gap to ~0.028" - same symptoms
- voltage drop between battery/coil inputs (not cranking) = 0.7-0.8V
- current drain with key on: ~7A, battery drops from ~12.3 to 11.65V (that should be ~75% charged)
- tried running off a car battery - some improvement (or just warm weather?), but still same symptoms overall (video)

Others:
- VCA done just recently
- Battery "feels" okay (cranks readily and for a while)

Todo:
- swap plug wires around (e.g. 2&3)
- check voltage drop/battery voltage as it is cranking (need to rig up a few clamps to do it safely and with airbox on)
- compression test (maybe - turns out I don't have proper size adapters, after all )
- Ford Escort coil mod - now that I have space under the tank cover (maybe, if a cheap set falls into my hands...)

The choke/enrichment is well.... for cold start purpose only, sorry but IMO only a retard would apply the choke when the engine is warm

Well, it's also yet another data point in a rather obscure problem. It's not like I'm trying to foul all four plugs on purpose...

[ranmafan]

More testing today:

Done:
- voltage at the coils while cranking - around 9.3V (at the same time, battery is around 10.5-11V - rather difficult to measure, though)
- voltage at the coils while idling = 12.8V (battery at ~13.5V)
- swapped 2&3 leads: no noticeable difference (at least, #3 didn't start flooding the way #2 did)

I should note that the same setup always started and ran fine with the original FZR head, even before going over contacts.

Here's one more odd point:
- just in case, pulled the carbs again, bench synced to perfection, ensured IMS are all at 1 turn out

However...
1&2 and 3&4 are now way out of sync (~100-150C vs ~250-270C). Accordingly, idle is too high, can't be brought down, and, blipping the throttle, RPMs hang for a bit Spraying starter fluid all over the place (airbox included) has no effect.

Getting rather confused here.

Todo:
- new set of plugs (turns out NAPA does have Autolite 4302)

[dru86]

Are you running the fzr or yzf600 ecu and with which flywheel? Did you use adjustable cam sprockets to get the cams lined up correctly with the crank? If not how far off were they?

Mine idled and started fine with stock internal yzf600 carbs after doing the conversion. Would start within 2 seconds with the "choke" pulled and given a blip or two holds around 4k. From memory idle mixture screws were set at 3.5turns. I'll see if i can get a video for you.

[ranmafan]

Are you running the fzr or yzf600 ecu and with which flywheel? Did you use adjustable cam sprockets to get the cams lined up correctly with the crank? If not how far off were they?

Mine idled and started fine with stock internal yzf600 carbs after doing the conversion. Would start within 2 seconds with the "choke" pulled and given a blip or two holds around 4k. From memory idle mixture screws were set at 3.5turns. I'll see if i can get a video for you.

Yeah, that sounds like the "normal" behaviour to me

All original FZR ignition and flywheel, YZF rods (3mm spacer), cams. Yes, I got adjustable cam sprockets and made sure they line up perfectly (although it does bother me that the intake alignment mark is in a different spot, compared to FZR...)

I'm thinking that messed-up timing would affect starting even when warm... wouldn't it?

[ranmafan]

Somewhere between disassembling/cleaning sparkplug caps, changing plugs (Autolite 4302. Yay.) and being extra careful with anti-seize, it's now a lot closer to "normal".

That is, consistently starts firing with a few seconds and even keeps idling (somewhat roughly) with choke on. Cylinder #2 still likes being cold - I can only guess it has something to do with configuration of the head and coolant tubes.

Here's what #2 sparkplug cap looked like inside...

All the other ones are shiny clean (no surprise, #2 is where any water would end up with bike on the sidestand).

[dru86]

Hey finally got a video of how mine starts, was waiting on a vacuum pump so i could replace the brick of a fuel pump that comes on the fzr. Did you end up sorting yours out? Here's the link to youtube