tzr250 6th gear problem

[dave o]

on saturday i went to pukekohe for my first race.
my bike wasnt ready so i took my road bike (tzr250 3ma) and it was great fun.
on the straight it wound out to redline in all gears but when i went into 6 the revs would drop and it would stop pulling.

i was wondering if changing the front sprocket so it revs out easier (and less strain on the engine?) would help fix the problem? i cant remember if it was sputtering or anything, but i dont want to fiddle with carbs just yet cos it was running primo in all the other gears. also not sure if i should put this thread in engine/gearbox or final drive forum so i just put it here.

any help would be good cos the next race day and the art day are fast approaching

[Jeaves]

Factory speed limiter or something?

[motorbyclist]

speed limiter? roughly how fast were you going?

perhaps the 6th gear is just an overdrive? use it much on the road?

[F5 Dave]

+1 there are a few sites around overseas that would have more info on bypassing speed restriction & or kit to buy. If it's std gearing (14/43) it would be made to rev out fully in top, then restricted by jap 180 thingy.

[Ixion]

3ma is the V twin? If so it's definately restricted (and crippled - ie 180kph and 45 bhp). And very hard indeed to bypass.

From memory the earlier reverse cylinder model was also restricted (bit academic since noone ever got the engine to stay together long enough to find out ), but easier to bypass.

[F5 Dave]

3MAs are reverse cylinder jobbie. They were restricted I'm pretty sure.

One of the sexiest bikes Yam made. But your smear on their reliability isn't without some anecdotal justification. The only two I knew people had blew in short order & it wasn't uncommon. I'd run the very best oil you can & check the PVs & pistons etc regularly. Quite a few have been popular for engine trransplants, but they are an odd layout so it makes it difficult.

I nearly bought one many many years ago but was ignored by the shop assistants so went elsewhere.

[dave o]

i would have been doing about 170 - 180ish i guess. speedo was disconnected so i didnt think the limiter would have been in effect? its the 3ma, with reverse cylinders. i think ive got a file somewhere saying how to get around the speed limiter, ill have a dig out. yeah its got standard gearing 14/43.

i use castrol tts and run it premix. its annoying taking a bottle of oil wherever i go on the road though >.<
i found a 300cc big bore kit for sale on the internet the other day ;D
theres some rzv500 engines in 3ma frames and turned into gp replicas which are pretty cool. when it blows up i might do that.

http://www.nkracing.co.uk/nkr11.html

[motorbyclist]

sure the limiter is attached to the speedo? (unlikely but possible)

make it do it again.... pay attention to wtf is actually going wrong perhaps?

[Ixion]

i would have been doing about 170 - 180ish i guess. speedo was disconnected so i didnt think the limiter would have been in effect?

http://www.nkracing.co.uk/nkr11.html

Restriction is driven from CDI not from speedo. CDI knbows revs and gear , works it from that. You can fool it a bit by fiddling the sprocket sizes, Wasn't premix originally

[motorbyclist]

how difficult is that restricter to beat?

in the nc30 you can pay big bucks for a box with a resistor in it, pay 50c for a resistor from DSE, or simply open the speedo and bend the tab that the needle hits when it goes to 180 out of the way

not that i would know from personal experience or anything

[Ixion]

Pretty hard. Not as hard as the V twin but harder than just a resistor or bending a tab (or connecting a couple of wires )

[motorbyclist]

sounds like a challenge

[dave o]

how difficult is that restricter to beat?

in the nc30 you can pay big bucks for a box with a resistor in it, pay 50c for a resistor from DSE, or simply open the speedo and bend the tab that the needle hits when it goes to 180 out of the way

not that i would know from personal experience or anything

my file says there's a tab in the speedo end of things you just bend out the way, but my speedo wasnt connected. my friend has some "maxpower" brand box or something that plugs in to the speedo. i dont know if he has used it or tried it out or anything, i could give it a go and see what happens.

[motorbyclist]

was the speedo cable not connected or the electrics not connected?

without the cable it would beat the restrictor, without the elctrics the restrictor should always be on

so i reckon you make it do it again and tell us what it was that was actually going wrong....

[stanko]

Restriction is driven from CDI not from speedo. CDI knbows revs and gear , works it from that. You can fool it a bit by fiddling the sprocket sizes, Wasn't premix originally

3MA has no gear position sensor, jap import engines are 45hp, speedlimiter is a tab in the speedo, disconnecting the sensor retards the ignition. Most of the 3MA problems have been solved. One of the main reasons they shit themselves is the wee inline filters in the carb inlet tubes fill up with shit then when the bike is going flat chat they run a bit lean as the float levels drop, remove the wee cone filters in the inlet of each carb and check how much crap is in them