mattb_uk

Well I took the carbs apart, all stock items and settings, glaring omission though....not one carb had a main jet in! I would imagine that could be my problem!

You'd think so wouldnt you, but I cant find the standard settings online have tried "yamaha thundercat standard carb settings", most things just come up about dyno jet etc. Its got Thundercat carbs but the airbox has been cut and shut to fit it under the tank.

Apparently, the carbs are all over the place! The dyno place got 26bhp out of it! yes, twenty six! I find that figure slightly odd as its never run THAT badly, and has had plenty of power up until the problem hits. Apparently there is an air leak and the main jets have been leaned off, needles raised, air screws adjusted etc, not sure why the previous owner did all that. What would people recommend? Just putting it back to stock setting and starting again from there? Does anyone know where I can find the stock settings? I have had a google and cant find much of any use. Cheers, Matt

Well, you were right, its not the battery! Im going to take it to the local dyno place and get them to look at it. I am away this weekend and am hopign to do a trackday with a mate on the 29th, but have a wedding the weekend before so I dont have the time to sort it myself, plus its startign to go over my head, fueling set ups etc! Thanks for all your help, I'll let you know what the result is!

Well, I had a play around with it all last night and although Its not cured yet i think im heading in the right direction. First things first, checked the battery connections and they were a little loose, i had a GSXR in the past that had a fault and that was just the battery connections not being as tight as they should of been. I hoped it would be as simple as that, it wasnt, but the symptoms were perhaps slightly better. Next I drained the old fuel, found a bolt in the fuel tank and drained the carbs. The float bowls all had screws that were basically only finger tight, if that, and some had fallen out alltogether. I have now taken them apart and cleaned them all and re-tighted all the screws. I then took it for another spin and it was a bit better, even pulled clean to about 10k in a couple of gears but not consistently. The symptoms now seem to be anywhere between 6k and 10k rpm. I will attach some pics in a bit, the modified airbox sits ok on the carbs but perhaps isn't the tightest fit it could be. My current thinking, is that it ran better the second time because the battery had a bit more charge from the first run, rather than anything to do with the carbs. Does this sound plausible?! It makes sense to me as the previous owner said it ran fine before and i probably let it sit for a while before i started it and have never taken it on a long ride. I currently have the battery off and charging, and will try it again later. Im trying to check the simple stuff first before i waste money on new electrical bits and bobs. Sorry if this is all a bit jumbled!

Hi Again, Thanks for all the advice, all sound logical so hopefully it is one of them. A garage evening tomorrow, so will let you know how I get on. Matt

Hi, yeah that was the first thing I did, I can only take his word for it but it was apparently running fine, and he did a few track days on the bike, the engine has only done 5k miles too. Matt

Hi, New member, im afraid i have already spent my first post in the technical queries bit so Im afraid this is my 2nd post, bad form I know! I've got a FZR400 with a 600 conversion, and used to have an R1 race bike until the big end went on it From reading the boards, it seems like a friendly place so hopefully Ill be seeing you guys and girls around! Cheers, Matt

Hi All, First post so, Hi! I've been racing CB500 and various other bikes for a few years but fancied somethign a bit different so got myself a FZR400RR with a 600 thundercat engine conversion. This was all done buy a guy who has done a few of these conversions and to my knowledge has all the required mods etc, and uses all the Thundercat loom and the tank sits higher to accomodate the thundercat airbox. Right, now my problem.... Stationary the big starts and runs sweet as a nut, BUT when i put it in gear and try to ride the bike it won't rev past 6k rpm. Getting up to 6k rpm it is as smooth as anything but hit 6k and its just bogs and barbles. Logic suggests its quite a simple fix but i have no experience of these bike really so not sure where to start. I have read about throttle position sensor problems but its so smooth up until 6k (and past in neutral) so that makes me think its not that. I could be wrong. Someone suggested it could be the carbs being block as when it draws from different jets one of these might be blocked? Could it be the ECU is knackered? Like I say, logic (mine anyway!) suggest that its something simple, a component failure of some kind but I have no idea what one? Any help greatly appreciated as am hopefully doign a trackday on it in a coupel of weeks! Cheers, Matt