4t tuning thread

[richban]

We've been through this before

True. Well I like the turbo concept. The cool thing is that you can use a water cooled engine. For a bit I thought you had to stay air cooled. Re read the rules and no cooling restriction is mentioned.

All I need is the engine and we are all go. Cut down v twin maybe. That way when it explodes the cylinder dead will just take out the front wheel not the tank and rider.

[TZ350]

True. Well I like the turbo concept.......

A supercharger driven by a slave engine........ we are working on one now.

[TZ350]

Actually when I think about it you could have a turbocharger driven by a slave engine.

The slave could be running hard out all the time driving the turbo, that way there would be no turbo lag when changing gear on the prime mover, constant manifold pressure all the time.

[Moooools]

True. Well I like the turbo concept. The cool thing is that you can use a water cooled engine. For a bit I thought you had to stay air cooled. Re read the rules and no cooling restriction is mentioned.

All I need is the engine and we are all go. Cut down v twin maybe. That way when it explodes the cylinder dead will just take out the front wheel not the tank and rider.

Vt 250 cut down and sleeved down.
I may just try that with my sidecar after I have spent some time riding it, if I ever finish it that is. Maybe I should try and get it done by the welly north island round. Fill in the gaps in racing...

[Yow Ling]

I have repaired a few FXR cranks. Seems there are 2 common failures.
Stiffies, where the bigend cage fails and the crank grinds to a halt, usually feels like fuel starvation or some tuning problem, then it siezes.

Then the less common but far more spectacular FXRmageddon, seem to happen at full noise, no warning just crunch. Seems to fuck the whole motor, hole through the top cases, sometimes the bottom, rod snaps in half, gear shafts bend. Sound familiar?

[Kickaha]

I have repaired a few FXR cranks. Seems there are 2 common failures.
Stiffies, where the bigend cage fails and the crank grinds to a halt, usually feels like fuel starvation or some tuning problem, then it siezes.

Then the less common but far more spectacular FXRmageddon, seem to happen at full noise, no warning just crunch. Seems to fuck the whole motor, hole through the top cases, sometimes the bottom, rod snaps in half, gear shafts bend. Sound familiar?

How many of those have you had now?

I had a type 1 which highsided me and got me run over on the Bren Bike

[Yow Ling]

How many of those have you had now?

I had a type 1 which highsided me and got me run over on the Bren Bike

Thats not my rod, I had one like that on my bike and repaired 3 others, sometimes the crankwebs are pretty ugly, not ones you would do on exchange.

Oh yea there is a 3rd kind of failure, when people remove the balance shaft and decide that the bearings are too hard to remove, they not going anywhere. Seems they do go somewhere, snapped rod and hole in front of motor

[kel]

Then the less common but far more spectacular FXRmageddon, seem to happen at full noise, no warning just crunch. Seems to fuck the whole motor, hole through the top cases, sometimes the bottom, rod snaps in half, gear shafts bend. Sound familiar?

So while I’m yet to witness the coming of Gog and Magog I do find myself living in fear of the FXRmageddon. While playing with cam timing I thought I had given the thing too much advance as it would hit a wall at about 10.5 to 11k rpm, set the timing back to standard but the problem is still there. This isn’t like the soft rev limiter the bike has at 12.5k which is kind of a machine gunning effect (if you hit it you know what I mean), it’s more of a hard limiter but the motor doesn’t seem to cut out electrically rather the power gives up and a hideous change of noise takes place almost like a bark (probably a better way to explain). Changed the rectifier and the CDI checked all the wiring and connections yet the problem is still there. Anyone else experienced this? Any help would be greatly appreciated. Cheers.

[Buckets4Me]

Any help would be greatly appreciated. Cheers.

get a 2 stroke

[Yow Ling]

So while I’m yet to witness the coming of Gog and Magog I do find myself living in fear of the FXRmageddon. While playing with cam timing I thought I had given the thing too much advance as it would hit a wall at about 10.5 to 11k rpm, set the timing back to standard but the problem is still there. This isn’t like the soft rev limiter the bike has at 12.5k which is kind of a machine gunning effect (if you hit it you know what I mean), it’s more of a hard limiter but the motor doesn’t seem to cut out electrically rather the power gives up and a hideous change of noise takes place almost like a bark (probably a better way to explain). Changed the rectifier and the CDI checked all the wiring and connections yet the problem is still there. Anyone else experienced this? Any help would be greatly appreciated. Cheers.

Not much goes wrong with them except big ends and a few bent valves, has it ever had a new big end? They go weird before they die

[speedpro]

They "start" out weird, silly 4-stroke things

[F5 Dave]

in every 4 stroke is two 2 strokes trying to get out.

[kel]

I have to admit to enjoying the banter but Im afraid the original question might get lost.

While playing with cam timing I thought I had given the thing too much advance as it would hit a wall at about 10.5 to 11k rpm, set the timing back to standard but the problem is still there. This isn’t like the soft rev limiter the bike has at 12.5k which is kind of a machine gunning effect (if you hit it you know what I mean), it’s more of a hard limiter but the motor doesn’t seem to cut out electrically rather the power gives up and a hideous change of noise takes place almost like a bark (edit: actually its better described as a cough). Changed the rectifier and the CDI checked all the wiring and connections yet the problem is still there. Anyone else experienced this? Any help would be greatly appreciated. Cheers.

[richban]

I have to admit to enjoying the banter but Im afraid the original question might get lost.

While playing with cam timing I thought I had given the thing too much advance as it would hit a wall at about 10.5 to 11k rpm, set the timing back to standard but the problem is still there. This isn’t like the soft rev limiter the bike has at 12.5k which is kind of a machine gunning effect (if you hit it you know what I mean), it’s more of a hard limiter but the motor doesn’t seem to cut out electrically rather the power gives up and a hideous change of noise takes place almost like a bark (edit: actually its better described as a cough). Changed the rectifier and the CDI checked all the wiring and connections yet the problem is still there. Anyone else experienced this? Any help would be greatly appreciated. Cheers.

Was it going ok before you played with the timing?

[kel]

Was it going ok before you played with the timing?

Pretty much, it used to suffer from the odd miss but I think that was due to not enough fuel in the tank as it never seemed to happen if I ran a higher level.