Smelly exhaust

[Jerry FS]

Hi guys, the work on my ZZR is coming on a treat, new seals new chain, sprockets, spark plugs, tyres. brake pads and disks, battery, oils and lubricants and a full re-spray.

One thing I have noticed however is the exhaust really smells strongly of fuel when I first start it up. Is this normal? My previous bike (Ducati Multistrada) had hardly any smell at all, possibly because it was fuel injected and the ZZR isn’t. ?

Do ZZR’s usually smell on startup?

[Mark]

Hi guys, the work on my ZZR is coming on a treat, new seals new chain, sprockets, spark plugs, tyres. brake pads and disks, battery, oils and lubricants and a full re-spray.

One thing I have noticed however is the exhaust really smells strongly of fuel when I first start it up. Is this normal? My previous bike (Ducati Multistrada) had hardly any smell at all, possibly because it was fuel injected and the ZZR isn’t. ?

Do ZZR’s usually smell on startup?

Carb bikes do normally smell of gas a bit from the exhaust, especially compared to fuel injected bikes. I know the ZZR1200 is factory lean, and many members add shims to the carb idle pins (is that the right term?) to allow more gas at idle, keeping the bike running cooler.

Did the previous owner do any carb shims or carb mods? When was the last time the carburetors were synchronized/balanced?

[Jerry FS]

Hi Mark, thanks for the reply. The carbs were balanced just before I purchased the bike a few months ago. No shims were added either. The bike runs really well after it’s warmed up and the throttle response is instant, it just stinks of petrol when it’s warming up. Fuel consumption seems about normal, only major (or minor) change I’ve made is changed the cog ratio on the sprockets (less brutal acceleration but better top end/fuel economy).

[CHARLIE]

Double check your oil level, making sure you don't have a float sticking. Upon looking
at it, it will be "too much oil" in the sight glass.The oil will also smell like gas as well.
Mine has had the shim thing done for years, doesn't change idle mixture but makes it run richer. It does have
a little bit of gas smell at first startup but kind of goes away after a bit. I'm thinking it is ok being it runs so well.
Also give her a once over with a really strong light to check for fuel leaks, there are a shit load of places it can
come from.Petcock, pumps, filter, lines and such. Let us in on what and if you come up with anything.

[BillDownUnder]

Too much choke at start?

[CHARLIE]

Too much choke at start?

Good point. I usually only lever mine about half way for startup, then after about a minute
cut that in half. I only run the fast idle/choke for about maybe 2 minutes or so.

[NATURALBORNKILLAR]

check that rubber pad that is just above the exhaust it can smoke and sometimes set the bike on fire !

[Jerry FS]

Thanks for the responses guys. Unfortunately the problems with smelly exhaust have now progressed to “won’t start when hot” I read the post about the choke slider on the carbs not returning or being misaligned being a possible culprit, unfortunately in my case it isn’t. I can’t find any electrical issues either. Plugs are new and the ht leads and coil pack doesn’t get hot after a long run. Once bike has cooled down it starts straight away and runs well. I’m a bit lost with what to do next.

[BillDownUnder]

Next possibilty - needles and seats in the carbs might stick open, possibly making it very rich at startup (ie flooding). If so, they need replacing.
BTW, how do the exhausts look - black and fluffy, or just a thin layer of soot?

[Jerry FS]

Hi Bill.
the exhausts look really clean, no soot or oily residue. The hot start problems are only recent, after a blast down the motorway last weekend (about 70 miles), I had to stop to fill up, that’s when I noticed hot start problems. After 10 minute cool down everything worked fine. When I got back home and bike was hot, same problem.????

[BillDownUnder]

Have you put fresh fuel in since then?
What air filter do you run?

[Mark]

Thanks for the responses guys. Unfortunately the problems with smelly exhaust have now progressed to “won’t start when hot” I read the post about the choke slider on the carbs not returning or being misaligned being a possible culprit, unfortunately in my case it isn’t. I can’t find any electrical issues either. Plugs are new and the ht leads and coil pack doesn’t get hot after a long run. Once bike has cooled down it starts straight away and runs well. I’m a bit lost with what to do next.

I had a similar problem but it was a fuel injected bike, 2006 ZX-6R. I wrecked it and got it repaired, and it had stalling issues ever since. Had it in multiple shops, they replaced spark plugs, wires, changed fluids, no change. It would always stall at some point after reaching operating temperatures.

I did my own research on the problem and found others stating they replaced their ECU and the problem went away. Sure enough, I ordered a used ECU on eBay, replaced it myself, and the problem never reappeared.

It might be worth getting a used ECU and swapping that if the problem persists and you can't figure it out.

https://www.ebay.com/itm/254231776158

[M.Rad.]

I'm with BillDownUnder on this one too, voting for stuck float valve on at least one carb.

You can clean the carb insides without removing the cables. You only need to pop them out of the spigots, twist the assembly around (careful not to kink the cables) and remove the bowls. Lay down a towel over the engine to catch spilled fuel and any parts that you drop. It is only necessary to remove the pilot jet, main jet, float and float valve. The internal passages can be "spray" cleaned with carb cleaner. Run a wire through the jets, spray out with carb cleaner. Gently clean the rubber tips of the float needle valve and use a Q-tip soaked in carb cleaner to clean the seat where the needle sits.
To test, attach a clean hose to the fuel inlet, turn the carbs upside down so that the float valves close, and blow into the hose (no, don't use the compressed air!). If they are sealing well there will be no air leakage.

Reassemble and re-mount. The hardest part (for me anyway) is guiding the ram air tubes back into the airbox.

I recommend that you not remove the carb tops and vacuum diaphragms unless you have a specific reason to suspect that they are damaged. They are easy to pinch and tear when reinstalling. Also, do not flood the diaphragm cavity with carb cleaner since it may soften the rubber. Blow it out gently with compressed air just to be sure.

Ta-Da! Nice clean carbs!

[Stevo555]

As noted before by Charlie ..... just make sure your Oil level in the sight window has not elevated , or weirder still is above the level of the sight window ..... I confess when one of my floats stuck open , at times I had a No Crank scenario .... hit starter and no crank turn. Starter engaged, but could not turn crank . A couple of times , before I understood the issue, the bike did start eventually, and ran with a very rich , gassy smell.... eventually the engine would flood and stumble on me , and again no start.... then I noticed the oil level was way up ... and found this forum ... the rest is history...
Pretty sure a poster named Danno saved me .

One other symtom, is my fuel pumps ticked excessively long when firing up the bike ... May not be this scenario , but a few things point in this direction.....

[M.Rad.]

Also, a stuck-open float valve can cause you to hydro-lock your engine causing a bent con-rod, cracked piston, etc. if the engine fires and runs the piston of a partially filled cylinder into the incompressible liquid. Be careful.