Author Topic: . (Read 6856 times)

PieEater · « **Reply #5 on:** 14 January 2018, 08:56:18 am »

Got to say that your carbs look very clean, almost suggesting that they've been out before and cleaned up, possibly you inherited this problem when you bought the bike !?!

I don't know how accurate your gauges are, it would seem to me that the pipes have pretty much the same amount of fuel in them the difference in levels could be explained by the distance from the carbs to where you are measuring the level being longer from the inside carbs (2 & 3) and shorter from the outside carbs (1 & 4). Rather than visually compare the height of the fuel level I would have thought you'd need to measure the length of pipe from its end to where the fuel level tops out to find any difference. You may be doing that or I may be missing something such as gravity affecting the fuel levels within the gauges.

If the coolant circuit has been bypassed and the 2 blue pipes are connected to the carbs and are not going anywhere you can just remove them, very weird that someone would have fitted them in the first place. You can tell if the coolant circuit has been bypassed by checking the right hand side of the radiator (connection just under the main pipe) and the thermostat housing just above the rad (connection coming off top left), you can see where I have capped the connections off on my bike, I have not bothered capping the spigots on the carbs as there is no point.

cl1ve2004 · « **Reply #6 on:** 14 January 2018, 09:48:49 am »

Another really interesting post..love this site !!!

agricola · « **Reply #7 on:** 14 January 2018, 05:12:36 pm »

The length of the tubes is irrelvant, gravity will ensure the levels in each carb are reflected in its connected tube

Mitch · « **Reply #8 on:** 14 January 2018, 06:22:10 pm »

Mitch · « **Reply #9 on:** 14 January 2018, 07:45:35 pm »

Falcon 269 · « **Reply #10 on:** 15 January 2018, 09:56:45 am »

Hi Mitch,

From your photo it looks as though you're checking the float height with the floats fully down, that's to say compressing the needle valves. If so, that's wrong and explains your float heights apparently being so far out.

Check out Pat's Site and the Ivan's Installation section to see the correct procedure for checking float heights. Whatever you do, don't make any adjustments until you are 100% sure that you are doing it correctly.

If the tangs on the floats appear unbent, then they will be at the standard OE position and this should give you the correct height. I have only ever found one float (out of thousands!) to be incorrect from the factory and that was a whopping 0.5mm out ...

Yamaha built the carb coolant circuit the same way from first model to last. Yours has been disconnected by a previous owner. It matters not where the blue hoses go but by all means trace them if answers your curiosity.

PieEater · « **Reply #11 on:** 16 January 2018, 08:46:02 am »

Thanks for your detailed response. I still think it's more than a coincidence that both carbs that are further away and have more distance for the fuel to travel are showing lower levels and both outside carbs with less distance for the fuel to travel are showing higher levels, but I've been wrong before and will be again $:\$

I'm wandering about how unburnt fuel would get into the oil? Presumably the mixture would have to be roughly correct and the bike firing on all cylinders or it wouldn't run properly. The only way I can think that this would happen is if one or more valves aren't seating properly allowing the fuel / air mixture to be forced into the engine on the compression stroke !?! I know your line of reasoning is that the floats are letting in too much fuel and dumping it but I can't see that the float bowl overflow would be routed to dump fuel internally rather than externally, that doesn't make sense. Unless of course the same hose gremlin that fitted your redundant coolant circuit hoses for no possible reason routed the overflow hoses incorrectly to an engine breather connection !?!

I take it you've checked the coolant levels to make sure it's not a problem with coolant getting into the engine? But if the bike has been running and the oil level has risen significantly you'd definitely notice the oil emulsifying and probably mayonnaise around the filler cap if coolant was involved.

As Cl1ve2004 says this is an interesting thread.

Ricky · « **Reply #12 on:** 16 January 2018, 11:00:37 am »

Hi, just thinking and I am very sure Mike would know but if your bike has such very low mileage it stands to reason that the bike has stud unused for a very long time, could this be a reason for some if not all your problems?
The carbs and the engine seals may have dried out?
Just wondering.

Hugh Mungus · « **Reply #13 on:** 16 January 2018, 06:17:40 pm »

Quote from: Ricky on 16 January 2018, 11:00:37 am

The carbs and the engine seals may have dried out?

If the float bowl seals have dried out and not sealing properly it can cause overflows. Worth checking.

Falcon 269 · « **Reply #14 on:** 16 January 2018, 10:12:18 pm »

The various seals in the carbs (and elsewhere) will tend t deteriorate with age rather than specific mileage.

Standing unridden/unstarted for long periods usually shows up as problems with blocked pilot jets/passageways, stale fuel and the like.

Like PieEater said, fuel overflows should drain to the outside (down by the right-hand footrest) and that applies whether the fuel is overflowing because of a stuck float or a leaking needle valve unit.

The airbox breather connects with the crankcase and that might explain a smell of fuel vapour in the oil but something would have to be seriously wrong for fuel to end up in the oil in any quantity. A high fuel level in the float chamber will show up as a rich misfire well before that, I would expect.

If the motor is generally fuelling and running OK, then there's little reason to suspect a problem of that magnitude.

Mitch · « **Reply #15 on:** 17 January 2018, 09:28:53 pm »

Hugh Mungus · « **Reply #16 on:** 17 January 2018, 09:44:02 pm »

Judging from your list of woes it does look like someone has been messing with the carbs.
Good luck...

Mitch · « **Reply #17 on:** 17 January 2018, 11:28:09 pm »

Hugh Mungus · « **Reply #18 on:** 18 January 2018, 04:21:58 am »

Sounds like you just need to do a full rebuild of the carbs.

Ricky · « **Reply #19 on:** 18 January 2018, 11:05:46 am »

I know hindsight is a wonderful thing, but would you not be better to but the set you bought off eBay on to the bike?

Falcon 269 · « **Reply #20 on:** 18 January 2018, 12:55:33 pm »

Hi Mitch,

I'll try to address most of your points in turn.

No choke required. Not unusual, particularly if the carbs have been rejetted or the mixture screws altered to 4 - 5 turns out.

Known issue, floats too high. Be clear on understanding here. They are invariably set correctly from the factory. Ivan alters them to achieve a better outcome with his jet kits. Yes, if left for extended periods on the sidestand, the fuel level in the lowest carb might get a bit high but it's not a big deal. Might mean that cylinder misfires until the level returns to normal. There are still thousands of bog stock Gen 1s out there and they're all running fine, just as Mr Yamaha intended. Well, most are ...

Oil level went up/down. Yes, that can happen without it being an indicator of fuel or coolant getting into the sump. These motors hide oil but a long lay-up can result in all of it draining down again.

Recent starting problem. Sounds like a simple misfire, reluctant start afterwards probably because battery voltage a little low. White smoke is usually condensation, topped up with a bit of excess fuel from the misfire. If it was a hydraulic lock, it would have stayed locked!

The carb overflow system is designed to prevent excess fuel getting into the motor. Stuck floats are quite common but you don't find reports everywhere of cylinders filling with fuel as a result. It does go out the overflows as it should. Trust me on this, I've seen it many times.

Same applies for fuel leaking past the float needle valve seat O-rings. You'll get a rich misfire long before that manifests as a fuel overflow, too.

If you are absolutely certain that the float heights are not right, reset them to 12.5mm. However, to be honest, I still have reservations about your checking procedure. You mentioned the floats barely seating the needle valve. That's not correct. The tang should just be touching the sprung tip of the needle, not compressing or seating it at all. If the tangs are obviously straight, then they have not been altered previously.

I suggest you sort out the other issues with the main jet installation, check the needles for type and installed height, fit new float needle valve seat O-rings, clean the pilot jets, put it all back together and see how she runs. Check the condition of your battery, particularly if you don't use an Optimate when the bike's laid up for a while.

I wouldn't bother with reinstalling the carb heater hoses. I've never heard of a Gen 1 suffering carb icing as a result of removing it. Too much hassle for zero return. By the way, there's no 'probably' about the carb heater system being the same on every Gen 1 from 2002 onwards ...

I can't help but feel you are over-thinking this and perhaps seeing issues where none exist. Sometimes the internet can be a hindrance as much as a help.

Mitch · « **Reply #21 on:** 19 January 2018, 09:31:58 pm »

Mitch · « **Reply #22 on:** 19 January 2018, 09:49:39 pm »

Mitch · « **Reply #23 on:** 19 January 2018, 10:24:44 pm »

Mitch · « **Reply #24 on:** 19 January 2018, 10:35:06 pm »