Tuning my fizzer

[riffer]

Hi guys. My fizzer has started to feel a bit rough in the last couple of weeks, and I'm hoping one of you guys will be able to point me in the right direction and hopefully save me some time.

Symptoms:

Really rough idle, needs a lot of choke to stop it from stalling, won't idle below about 2500 rpm.

Seems a bit "woolly" on the first bit of the throttle, but once it gets to 4000 its like it clears its throat and gets going.

Stalls a bit at lower revs.

A smell of petrol from the bike.

I'm thinking it could be seals in the carbs stopping a perfect vacuum, however I'm open to any possibilities.

I haven't checked the plugs yet. Or the Air Filter.

I've had the bike for 7000kms now, done and oil and filter change and adjusted and oiled the chain regularly has been my maintenance so far.

The bike is a 1987 Yamaha FZR750RT 2LM, with 48,000km on the clock. Doesn't seem to be any camchain rattle, so I've ruled that out at present.

Am I on the right track?

[wkid_one]

Running rich?

[Slingshot]

Sounds like my problems...which I think is caused by crap in the carbs, I'm stripping mine down this weekend to give it a good clean out so I'll let you know how I get on.

[merv]

Yeah could be crap in the carbs but if it smelling of fuel probably one or more are suffering from too much fuel usually caused by float needle problems i.e. worn or crap in them allowing too much fuel into the bowl. However, that wouldn't tie in with needing the choke on which implies the opposite - running too lean. Does it have CV carbs and could you possibly have a split diaphragm in one of those? Sounds like you need to have a thorough look at all the carbs to see what is wrong. Symptom of split diaphragm is usually a gutless engine slow to pick up speed.

[riffer]

Symptom of split diaphragm is usually a gutless engine slow to pick up speed.
It's not exactly gutless - after 4000rpm it pulls well. I'm just finding that I'm using more throttle than I usually do now. They are CV carbs I think - Mikuni BDS34's.

Sounds like shit in the carbs though. Over Xmas the bike sat in the garage for two weeks and I think this may have caused the problem.

[riffer]

Is it possible that the petrol smell is caused by petrol going back through the breather tubes?

Which would indicate float level problems I guess...

[pete376403]

A mate with a 1200 Trophy had a problem similar to this (Wgtn M/C couldn't fix it, either). Was a split diaphragm in the vacuum fuel tap, was leaking fuel down the vacuum pipe into the inlet manifold.
Gas mileage was crap, low end running was uneven and in spite of the obvious over fuelling, gave the impression of running lean (?!) :doh:

[riffer]

A mate with a 1200 Trophy had a problem similar to this (Wgtn M/C couldn't fix it, either). Was a split diaphragm in the vacuum fuel tap, was leaking fuel down the vacuum pipe into the inlet manifold.
Gas mileage was crap, low end running was uneven and in spite of the obvious over fuelling, gave the impression of running lean (?!) :doh:
Pete - sounds like I may have to bring the bike over to show it to you mate, seeing as you're a stone's throw away. I'll pm you about it...

[wari]

A mate with a 1200 Trophy had a problem similar to this (Wgtn M/C couldn't fix it, either). Was a split diaphragm in the vacuum fuel tap, was leaking fuel down the vacuum pipe into the inlet manifold.
Gas mileage was crap, low end running was uneven and in spite of the obvious over fuelling, gave the impression of running lean (?!) :doh:

I've had the same problem before tiday ...

[Slingshot]

The smell of fuel could be caused by a stuck float or needle valve letting to much fuel in and therefore fuel hitting the overflow and pouring out.
If you can see the bottom of the carbs you may be able to see the fuel coming out. Start the engine and see if you can see it.

I took my carbs off last night and it took about half an hour, that including removing the tank & airbox.

The carbs themselves came apart pretty easy too.

[Motu]

How do the carbs attach to the head? with stubs is most common....check those,often they are bonded to an alloy flange.Mine were no longer as one piece,so rebonded them with indusrial strength urethane,good as new.The symtoms are as you describe,poor idle but good top end.

[merv]

OK if its got a vacuum fuel tap I wasn't thinking of that but as Pete says that could be a problem too.

Sitting the bike for 2 weeks shouldn't hurt - usually got to be parked up for months before it really causes a problem - except for that issue I have talked about before with this modern unleaded fuel. Then the problem is hard starting unless you drain the carbs first but once drained once the bike runs fine and the carbs aren't crapped up with dried fuel. As I say that takes months not weeks.

[gpercivl]

I'd check the plugs and air filter before doing anything else...a partially blocked air filter can give all the symptons you've described plus lead to plug fouling.

[riffer]

I'd check the plugs and air filter before doing anything else...a partially blocked air filter can give all the symptons you've described plus lead to plug fouling.
I think you're spot on there. I pulled the plugs on Saturday. What a prick of a job to get to those inner plugs! Anyway, managed to change them without stripping the plugs, and put some new ones in.

Plugs are completely carbon fouled. Bike is running a whole lot better - in fact I did my first ever off-the-throttle wheelie on Saturday road testing it!

So I'm picking up a new air filter today (Maindstone Yamaha didn't have one on Thursday) and I'll put it into the bike on the weekend.

The bike seems to pull harder and cleaner now, particularly off the throttle, however the idle is still dodgy (varies between 2000 and 5000). Still, I will withhold doing anything to the carbs until the air filter is changed.

[Slingshot]

How long has it been since the plugs were last changed? And did the problems start all of a sudden or have they been getting progressivly worse.

The reason I ask is that there maybe something causing your plugs to foul up, if that's the case you may have just fixed the symptom not the cause.

[moko]

If your plugs are carbon fouled you might need a re-bore,or at least a new set of rings and a de-coke.

[riffer]

If your plugs are carbon fouled you might need a re-bore,or at least a new set of rings and a de-coke.
oOOER. Now you're getting me worried. Maybe I'm not describing the plugs well. They look just like what would happen if the bikes running rich.

I don't think it needs rings. It doesn't use oil.

Power doesn't really seem to be down. The fact that it wheelies off the throttle without pulling on the bars or clutching it makes me sure theres a reasonable amount of power.

I will check on the air filter this weekend.

Bike has done 48,000kms. Its a 1987 grey import 2LM model from Japan. I bought it from Motorcycle City in Lower Hutt. They told me it had been serviced, but to be honest, it hasn't.

Middle plugs had rust on the top, some of the centre pins are burned right down, and the gaps were completely wrong.

Also, I did an oil/filter change in the Xmas holidays just because I wanted to, and the stuff that came out was black as coal and runny to boot.

So I think it's just hasn't been serviced like I was told. Too bloody late now to take it back and bitch about it.

I will be checking a number of things about it now though.

1. Air filter
2. Brake pads. Just discovered the back pad is damn near completely worn.
3. Brake fluid. Who knows what state that's REALLY in.
4. Anti-freeze. Knowing my luck, there's probably just water in there.

Oh well, at least there's no fork seal leaks (touch wood)...

[merv]

Bike has done 48,000kms. Its a 1987 grey import 2LM model from Japan. I bought it from Motorcycle City in Lower Hutt. They told me it had been serviced, but to be honest, it hasn't.

Yep where do salesman rate? - that's right they are bottom dwellers down there with the lawyers.

Carbon fouled plugs on a 4-stroke is not a normal problem but maybe this bike spent its life running round Tokyo with the choke on who knows.

Sounds like you are on the right track - go over the thing from top to bottom making sure it is all well serviced. Replace the brake fluid, radiator fluid, air cleaner element etc and make sure its all up to scratch and then you can be confident its done.

[riffer]

Sounds like you are on the right track - go over the thing from top to bottom making sure it is all well serviced. Replace the brake fluid, radiator fluid, air cleaner element etc and make sure its all up to scratch and then you can be confident its done.

OKay, I got the replacement air filter and decided to replace it tonight.

Unfortunately they gave me an FZR1000 filter which is elliptical and my FZR750 takes a round air filter, so they're trying to track down the right one for me. Never mind, good experience for me in taking the tank off and I got to see the air filter. and check out the airbox and have a quick look at the carbs.

So, the air filter is a real dark grey inside, and smells kinda petrolly, but not really. This is probably normal I guess. Anyway, it definitely looks like it needs replacing.

Airbox looks ok, no cracks etc. The clamps which hold it to the carbs needed tightening, which I've done. There's no real signs of leakage from the carbs, with the exception of no2, which has what looks to be a kinda of varnishy leakage around the bowl, which I'm picking could be old petrol, maybe. If the float is incorrectly set, could petrol leak out of the carb through some kind of overflow pipe, and go over the carby? Excuse my ignorance, carbs definitely ain't my area of expertise.

So I reckon I'll replace the air filter and do a few more things, and then when I have a few more $$$ look at the carbies.

After buying a race stand, four new plugs and an air filter this week, funds are a bit tight. Ah the joys of having three young children and a mortgage!

Oh, and I checked the overflow on the coolant. Well it's kind of light orangey and smells like slightly rusty water. But I can't remember if ethylene glycol has a smell, so I'm not sure if this is just water, but anyway, next payday (I get paid once a month last day of the month) I believe it will be time for a coolant change...

Anyway, I know this sounds like a real hassle, but I'm deriving a large amount of satisfaction from doing all this. I can understand the pleasure some of you get from working on your own bikes.

[merv]

Glycol has a funny sort of sharp smell - quite distinctive - and it feels kinda oily if you touch it unlike rusty water which won't feel that way. Some coolants are an orangy colour but in the main green seems to be the normal colour. I buy my coolant in 4 litre packs from Repco for a good price.

I would say the problem with your bike is it just has sat round too much between its life in Japan and the time you bought it here. I had a squizz in Motorcycle City's window a couple of weeks back and there are bikes in that showroom that were there over 4 years ago. Unless they have been hired out they won't have gone anywhere.

[merv]

p.s. forgot to say if it has a paper air filter did you ask about getting a washable foam filter? Many years back at the first check of the VFR's air filter I bought a Unifilter (think that's the brand) because a replacement paper filter was too close in price compared to the foam filter. Just buy the cleaner and oil aerosol cans to go with it. Then costs virtually nothing to keep clean after that, just the fun of your labour caring for your baby. I was used to foam filters because of my dirt biking and had no worries changing the type.

[riffer]

p.s. forgot to say if it has a paper air filter did you ask about getting a washable foam filter?

Yeah, the one they got for me was a hiflofiltro www.hiflofiltro.com and they are looking at one for me now. Could be that the only one they can get me might be the genuine Yamaha part but here's hoping not as it might run to 80 bucks :crazy:

Interestingly, the guys at Sawyers were quite adamant that under no circumstances should I use anything other than the genuine Yamaha part as any other filter will mess with the air flow in the airbox - I'll take that with a pinch of salt...

[merv]

So right, it was Sawyers that sold me the Unifilter - Carl was the man back then at the parts counter but now he's at Motorad and they are all part of the same family anyway. The VFR runs as crisp as you can imagine a bike should and there was absolutely no perceptible difference with a foam filter. Back then the comparo was something like $75 for the Unifilter and about $50 or more for the genuine Honda paper one so the choice was easy for a tight arse like me.

[riffer]

OKay, I got the right hiflofilter and chucked it in the bike. Piece of cake - especially as I had rehearsed it the day before with the wrong one :rolleyes:

First impressions weren't marvellous - especially as the weather was pretty shite yesterday - but as the ride wore on it was like the bike had cleared its throat.

The new filter is different to the old one. Two main differences:

1. The filter mesh. Previous filter had what looked like real fine chicken wire mesh. This new filter has no mesh, just looks like light metal with large holes punched out of it to let more air in I guess. Anyway, there's a pic attached so you can see what I'm talking about.

2. On the old filter at the top there was like a rubber collar that extended down into the air filter which would have restricted the air flow a bit more than the new one, which doesn't have it.

So, apart from those differences, it's a good fit and sounds cool.

When I am revving up the bike at a stop, the airbox shakes a bit now, and throttle response is much more crisp. There's still a little bit of a hesitancy, but I can ride it now from 2500 rpm up. It's very smooth in response now.

I thought the bike might have been going a bit slower but a takeoff from Melling lights today going full throttle through first three gears proved me wrong on that - yippee (sorry officer - testing bike....)

There's a cool new induction noise - sort of a wworrrrr from 6000 upwards which is absolutely addictive. I'm finding myself riding a couple of gears down just to hear that noise :bleh:

So next steps I guess, replace the fuel filter this weekend. Then maybe clean out the carbs (just to be sure) and do a coolant change.

Cheers for all the help guys.

[Redstar]

:mellow: Hope it gets sorted. My opinion is that the plugs carboned or oiled up like really black indicates the Mixture is too rich? especially if all four are so?rings probably not yet an issue :mobile:
the air filter was a cheapish move and hopefully will make a difference but I had a CX500 and it was a similar problem but plug cleaning only gave temporary relief. it turned out to be the rubber vacuum diaphrams :eek:
diahrams are very unreliable :buggerd: condoms are better!
anyway that and worn neddle jet sliders. I dont know the design of your carbs but rubber perishes with Kiwi petrol after Japanese stuff.
I lived I japan for two years someone said about the traffic in Japan and slow riding around. this is a myth the Japs dont use their bike during the day well not 750s anyway only at night on empty roads or at weekends.
one thing they dont do is service the bikes so apart from the warrenty and compulsary warrent service every two years they just chuck them away when they stop. then we get them.I saw heaps of abandoned bikes and a flat deck truck would go around and collect them.
You can generally trust the odometer of grey imports but not the service history. I fitted a uni cut and glue filter to my bike and soaked it in the proper Oil guu I used Bostic to stick it in the frame and its fine.
You have a cartridge filter so UNI not applicable.
If you still have a problem check the neddle slide wear and vac diaphram if it has then have the float levels set and balance the carbs and your set for life.
I would take it to the shop for this and find a cheap deal
let us know how you get on.

[merv]

[QUOTE=Redstar
diahrams are very unreliable :buggerd: condoms are better![/QUOTE]

Geez how many times have you used a condom over and over to compare it to the use a carb diaprhagm gets? Wash it out each time?

[pete376403]

I wouldn't put too much emphasis on plug colour. Now that there's no lead in the gas they don't get the nice light tan colour that the correct F/A ratio used to give. Forex sample, look at exhaust pipes - they used to go quite light grey, even white when mixtures were correct but now they remain a sooty black regardless.
Proabaly the only sure way to adjust mixtures is with a dyno and gas analyser, neither of which is common home workshop kit.
You mentioned the plug centre electrodes were worn down - that wouldn't have helped. Partial compbustion and maybe a bit of backfiring through the carbs could account for the petrol smell (and the shitty running).

And the comment about Motorcycle City - a friend sold them a F650 BMW about 6 -7 months ago. Its still there and they want waaay to much for it

[riffer]

Okay guys - now I'm looking for a tool.

A T-stem nut wrench and bearing adjustment spanner.

For example:

http://www.motorcycle-superstore.com/item.aspx?style=7964&department=646&Division=6#

Anyone know where I can get one of these (Yamaha - 30mm) for a good price or even borrow one for the weekend?

I've got Sawyers looking one one for me but I daresay it won't be cheap.

Cheers

[riffer]

I've cleaned out the carbs and jets and now have a great idle on the bike.

Previously the bike wouldn't idle without the choke on AT ALL, and was rough as guts under about 3500, where it would clear its throat and take off.

Power delivery after that seemed strong but the airbox was noisy (which I didn't mind).

Now the bike's idling nearly perfectly at 1250 (recommended idle according to Haynes manual) and choke is not needed at all. In fact if I try and use it, the bike dies.

Power delivery is VERY smooth, particularly off idle and I can go around slow roundabouts at 2,000 rpm without having to clutch it any more.

An unexpected side effect. Previously I was getting 180km before hitting reserve.

Now on my first tank after tweaking the carbs, its got to 255km and not hit reserve yet.

Was my bike running that bad? I guess it was. The power is a lot smoother now. Airbox is quieter. In fact it seemed so smooth I was worried it was a bit gutless - you know how it is - when its running nice it seems slower - but its definitely not - timed runs rule that out (very rough timed runs though).

I haven't checked out the plugs yet but there definitely seems to be less carbon buildup at the muffler outlet so I hope I'm on the right track. Of course I could be running too lean now but I guess there's no way to find out without checking the plugs.

Just the steering head bearings to do and I may be happy with the bike :)

[merv]

Its great what a bit of TLC produces eh!

[TonyB]

[QUOTE=celticno6]Hi guys. My fizzer has started to feel a bit rough in the last couple of weeks, and I'm hoping one of you guys will be able to point me in the right direction and hopefully save me some time.

Symptoms:

Really rough idle, needs a lot of choke to stop it from stalling, won't idle below about 2500 rpm.

Seems a bit "woolly" on the first bit of the throttle, but once it gets to 4000 its like it clears its throat and gets going.

I'm thinking it could be seals in the carbs stopping a perfect vacuum, however I'm open to any possibilities.[QUOTE]

I have only had time to read your original post, so appologies if this has already been said: Not quite the same problem as mine, as my FZR1000 would idle roughly and would have a stuttering missfire up to 3k rpm. The problem was mostly caused by the slides in the CV carbs wacking fully open as soon as a bit of throttle was applied which reduced the vacuume to almost nil. I say 'mostly caused' because the problem isn't completely cured. The bike always works fine over 3k rpm. Another classic problem with the Mikunis in FZR's is the emulsion tubes (needle jets?) getting worn, which makes them run rich at low rpm, but this doesn't sound like your problem. Have a look at the slides.

[riffer]

Thanks Tony. Sorted a while ago. I have, however, introduced and mostly solved many problems to my bike since then. ;)