Hello there.

Hey, this is OB from manchester. Just bought a thundercat after successfully completing the DAS. 2001 10k miles.

Been riding it for a month. I am getting bad fuel economy 120m till the light comes on. Ive also recived two different information about how much the tank holds. Does the tank hold 19ltrs plus reserve of 3.1 making the total capacity 22.1 ltrs. Or does the tank hold 19ltrs minus 3.1 ltrs reserve making it 15.9 ltrs. Someone also suggested that something might be up with the carbs ?

Secondly I have been having trouble downshifting, it is sticky. Sometimes I cant shift down untill i let the clutch out a little and then I hear clunks. Not at smooth as it is upshifting.

I have been on the YZF forums and they reckon it is a bent shift shaft. Have a look at this, I made this yesterday to make it a little clear https://www.youtube.com/watch?v=8XmZUrd3758

Anyone have any advice on this ?

hi and welcome mate, im in Oldham and theres a couple more locals too.
120 til light comes on is bad, I get 170 at least, even if ive been caning it. prob is a carb issue but im sure someone else will be in who knows about that stuff.
try get out on one of the rides that the forum members organise, they are excellent. I even do smaller rides to Derbyshire 100 odd milers when weather is nice and I have time, youre welcome to join me sometime
chris

Welcome aboard  

Hi OB  

Fuel economy could well be down to carbs. The Gear thing could be down to something as simple as an oil change, or chain tension or clutch cable adjustment/lubrication.

Your fuel tank holds 19 ltrs, . . that includes 3 - 4 ltrs reserve. there are many threads on the forum about tank range, but on average people seem to get 175 to 185 miles (from full), to reserve light on. That'd give you 30 to 40 ish miles on reserve.

A bike (any make), with so few miles on the clock (if genuine), should not have anything majorly wrong with it. So if you're not confident with the old spanners, book the bike in with your local bike shop and get them to give it a good service and refresh.

 


EDIT:

From your youtube, it sounds like your carbs are way out of adjustment, and would benefit greatly from some TLC and balancing.
The gear thing still could be clutch adjustment. Spend a few bob on a knowledgeable mechy and she'll be right matey . . . . The cat has a great motor, , , have a wee bit of patience, it'll all fall into place  
Have a snoop in the Workshop area

Thats what i read on the internet so I serviced the bike. Well not complete service, changed the oil and filter. I also re tentioned and oiled the the chain. Was planning to change the spark plugs and have a look at the air filter at some point but the forks had some pitting which sheared the seal off so that took precedent. I did a bodge repair on with the famous epoxy technique and changed the seals and oil. It was a pain in the bum, damper rod was jammed stuck and the bolt was threadlocked.

So yeah I have done the oil change and lubricated the chain but it hasnt improved the shifting.

I think the mileage is genuine considering the last 6 years MOT have only 1000 miles on it.


The clutch seems to have 2.1mm of freeplay on top, I havent had a chance to see the bottom adjustment. If you see the video, it is shaky you would know what I mean. I tap and it doesnt down shift, then I let the clutch out a little and tap and it shift but with a clunk.

The guys on the YZF forum seem to reckon its a bent tab on the shift shaft. New shift shaft is 60£, used is 15£. I'd probably get used, short of cash and will have to change the oil again anyway if I am taking the clutch assembly off to gain access to it. So about 25£ expense.

So the full capacity is 19 ltrs, So basically 50mpg till the light comes on. I filled 15.2 ltrs last time when the light came on and that got me 121 miles.

Hi and welcome.

Your idle is a bit low (1200 RPM).

You say shaky? that the engine vibrating? If so I'd say carb need balancing*, air cleaner check and have a look at the plugs. You'll see my fuel consumption below and it is lower than what it has been - depending on how the bike's ridden I should be getting closer to 60mpg.

* when riding do you feel a vibration through the handle bars and maybe foot pegs - these are signs of carbs out of sync.

It is supposed to be between 12 and 13 hundred rpm isnt it ?

Shaky as in I was trying to capture the downshifting issue while holding the camera while keeping the clutch engaged, not fun. Should have asked someone else to do it.

There is vibration, but I dont feel anything too different from the training cbf600 I used whilst training. I will check this when I am on the bike next time. Probably cant do it for a few days since I am busy working.

Old cat thinks the carbs are out of sync. I was hoping there isnt much expense coming up with the bike. Looks like next on the agenda is to get a carbtune and learn how to sync carbs, hah! and while I'm at it, check the air box and the spark plugs as well. I'll have to wait a few weeks to do this after I get paid at the end of the month.

Ah well OB,

It seems you're no stranger to a bit of spannering, and therefore braver, more knowledgeable than me.
Bobh or Tee-Forty (among others), would probably be best placed to help/advise you. I was going on what others have muted on similar problems in the past. In the meantime, you may benefit from having a look in the workshop area of the forum (I put the link in my last post), you'll find all sorts of hints and tips . . . inc. carb balance etc. etc.

Good call with the plugs, sounds to me like a cylinder or two are misfiring on the youtube, hence my comment on carb balancing.

Cheers

Yeah, I can spanner a little bit.No expert by any means. I am new to bikes, but I am trying to learn things as a go along. This was my first oil change ever and I had never even dismantled a fork before last week. I got a bargain when I bought the bike for 1k, well I think I did anyway, haha. But I also expected a few niggly issues, its just that slowly the expense is piling up. However I could have spend 2k on a bike and had the same issues. You never know.

I am only trying to fix these things as I plan to keep the bike for a few years at least. You are kind when you say more knowledgeable, because I had no idea the carbs were out of sync and needed balancing. But you did, eh!

I will definitely have a read through the workshop link.

Yeah, If I have the tank and the airbox off I might as well change the plugs then and there. Because changing them with the fairings on seems like and impossible task to do with the radiator hose in the middle.

Thanks for your input.

You're welcome,

You'll find we're a friendly lot, . . . mostly insane, but on the whole, alright  
Any questions you can't find the answer to on or in the forums . . . then pipe up, someone will know the answer or provide you with a link to the info.

There's also a couple of "characters"  around (yours truly inc.) , that may from time to time pull yer leg . . . but I'm sure you can hold yer own

And you're quite right about vehicle ownership. From the moment you buy, to the moment you sell, it'll rob yer wallet blind one way or another  

Yeah, these are the only two main issues really. The sticky downshifting and the bad fuel conomy.

What I am actually wondering; out sync carbs can cause that bad fuel economy ? Because I'm only getting 35mpg.

Poor carb balance, bad jetting, a gummed up air filter plus fubar'd sparkers, . . will all add up. That and the human natural reaction to twist open the throttle to compensate for said faults . . . . yeah, could well be the root of your high fuel usage and low mpg.

Oh, . . and don't forget . . . . we're heading into carb icing season now too !!!

Hopefully I wont have to clean the carbs and it is a simple service that the bike needs (sync, filter & plugs). Because that looks like a complicated procedure to take the buggers out.

But even then I need to sort this downshifting issue out. Its got me into a few sticky situations where I should be in a certain gear but it wont downshift, then it splutters and I almost stall the bike because it wont pick up in 4th gear.

Btw, do I change the air filter (new) or should I just clean it (old) with some solvent like it says in the manual ?

I was actually reading up about carb icing, winter is coming afterall.

Also I was looking, there are a few tcat members around manchester.

Hi & Welcome

I think most of the 'fixes' I would have suggested have already been covered - oil change, chain adjustment, carb balance.

No idea about the bent shift shaft. It does sound painful though.

Air filters aren't that expensive £17ish.
It would certainly rule out another unknown as an engine starved or air won't run smoothly.

You may do this already but try blipping the throttle as you change don might help.....it at least sounds good.

Good luck

Cheers
Rosco

Hey OB welome to the forum bud. Sorry to hear of your woes with fault finding.

I had the same problem with sticky/cluncky gear change when I changed my engine on the 'cat. This was solved by adjusting the bottom clutch end and then I changed the clutch cable as this wss old and had too much play.
Tis much better now and very smooth gear change.
Cable is around 20 quid and if you can change a push bike brake cable you'll definitely be able to change it on your bike. Same principal.
I've also got the same engine noise and fuel economy as you and like the guys have said it' definitely carb syncing needed.
I was lazy and bought another bike lol but still got the cat and gonna sort it over the winter.
Good luck and have fun getting dirty. It'll be worth it in the end.  

It is just downshifting that is sticky, upshifting is fine. Never misses a shift. Plus someone also said I should try downshifting above 3k rpm. So I will do that and blip the throttle.

At first, I will try to do the clutch cable adjustment, maybe a new cable. If that doesnt fix it, then I will open the clutch box to see if there is any damage on the shift shaft. Apparently if you are having trouble finding neutral then thats what it is. I did have trouble finding neutral in the beginning but its not too difficult now. However finding neutral from 2nd gear is impossible, nightmare. So I always shift into first then feather it into neutral.

I will look into doing the cable adjustment, filter, plugs and carbs balancing this week. Lets see how that goes, if this rain ever stops.  

Hello OB welcome... 

Hi OB and welcome to the forum, as you've probably already noticed we're a pretty friendly and helpful bunch on here. I'm based in Oldham and if at any point you need help with any of the issues I'm always glad to lend a hand. Balancing the carbs will make a big difference to the fuel economy and general running of the bike. If you're happy the chain is correctly adjusted and you've changed the oil etc I'd be inclined to check the bottom adjustment on the clutch before delving into more intricate (and expensive) fixes.

Best if luck

Steve

Hello and welcome, sorry you're having to deal with these issues!

Carb balancing is pretty simple to do, well worth getting the Haynes manual if you haven't already. You can buy a cheap balancer on ebay, I think I got mine for about £15...

Just out of curiosity what grade oil did you put in the bike? The cat is known to be "fussy".

Whilst you're down at the sprocket cover checking the clutch cable also check your front sprocket isn't loose (can be quite common).

Good luck

Paul

Yeah I will check the clutch and the sprocket.

I put 10w40 semi synth api sl/cf grade oil. Better than what yamaha recommends (sf, sg, sh).

yeah the balancing is not hard, I do have a pdf copy of haynes. Balancers are expensive. 40£ and above, I might build a manometer. i have to wait for the parts to arrive anyway. I have ordered the plugs and the filter.

Oh, and it also says apply oil to the air filter. Whats that all about ?

Applying oil stops the filter from drying out and deteriorating. I replaced mine (when I had a cat) with a K&N which you still have to oil but with their "special oil".

The clutch on the cat can slip if you use really good oil, you are using the right grade which is the important bit.

Crikey you're right about the cost of balancers (just searched) they have gone up since I bought mine!! You could even just buy a 1 or 2 cylinder balancer for the job? will just take a bit longer.

Check all the seals/gaskets around the carbs where they sit on the engine and check the air hoses (sorry forgot what they're called) for the ram air system is attached or if you have any obvious leaks as you don't want to waste your time balancing!

Sorry if this seems obvious.

Cheers

A you could you could also check the headers for corrosion. The original Yam ones were made of chocolate and most end up replacing them eventually with stainless steel ones.

Any holes in them can cause dodgy running/fuel issues.

Good luck and hope you get it sorted.

Yeah I made sure there were no friction modifyers in the oil. So I think the oil is alright. I will see what I can do about the balancer. And I will have a look at the air system to see if there are any issues there.

Headers are alright actually. I dont know if the downpipes are stainless steel. But their colour is yellow currently.

I tried downshifting by blipping the throttle. It is a bit better but still hit and miss. I still have to let the clutch out a little bit away from the handlebar for the downshift. Plus I got soaked in the rain, hah!

What gear do you guys mostly stay in when pootling along at 30mph. I currently ride around in 3rd. Try keep the revs above 3k. But I do need to get me some earplugs.

Ear plugs at 30mph? it looks like you have standard can?!

I would check your downpipes all the way along and they shouldn't be yellow.

Sorry I wrote the above on my phone so was a bit blunt...

You shouldn't need earplugs at such a low speed, even with an aftermarket can. Yellow downpipes would indicate the possibility of corrosion I believe they would also be original which are alluminium if I'm not mistaken.

I would check the bottom of the bike as the pipes are exposed and are subject to stone chippings, if it's noisy it could mean you have holes in them! I had this problem with my current bike which as Snowcat pointed out can lead to fuel problems and can aid with knocking your carbs out of sync (something to do pressure).

Worth taking the pipes off if you get a chance for a proper inspection as holes can appear in the most unlikely of places.