FXR150 conrods breaking

**Bren_chch** · 30th December 2008, 23:06

'cam timing' You slotted your sprockets? thats COOL!

**Sideways Sam** · 30th December 2008, 23:30

Originally Posted by Bren_chch

'cam timing' You slotted your sprockets? thats COOL!

To tell you the truth, there's no option if you've adjusted the deck hight.....

The difference between teeth on the sprocket must equate to about 16 degrees of crank or more. After my deck milling job (to suit weird and wonderful piston) factory timing was half way between 2 teeth!

The timing is very cool though, you can tweak it for for different rev ranges..... Would be an interesting adjustment between different tracks....

Have you ever played with injection and management systems? That will be my next project, rather than replacing the carb.... Then there is even more adjustments to play with.....

**Buckets4Me** · 31st December 2008, 07:59

cant wait to see what you turn up with next year now
Tim Richard Olly Karl Dave you guys had better watch out

**bucketracer** · 31st December 2008, 08:57

Originally Posted by Sideways Sam

To tell you the truth, there's no option if you've adjusted the deck hight.....

The difference between teeth on the sprocket must equate to about 16 degrees of crank or more. After my deck milling job (to suit weird and wonderful piston) factory timing was half way between 2 teeth!

The timing is very cool though, you can tweak it for for different rev ranges..... Would be an interesting adjustment between different tracks....

Have you ever played with injection and management systems? That will be my next project, rather than replacing the carb.... Then there is even more adjustments to play with.....

And I thought 4 strokers were becoming boring and pedestrian with all those same-as FXR's. This project is starting to go some where. A talented rider/developer who has a few clues, combo, this is very very interesting. Do keep us informed of progress.

**nudemetalz** · 31st December 2008, 12:47

I know this is going to be a "so what" question, but what Loncin ones were fast there?
I'm currently modding mine to try to keep at present.

**dangerous** · 31st December 2008, 16:14

Originally Posted by Kickaha

Where are the rods breaking, are they all doing it in the same place?

mine was at the bottom...

**Bren_chch** · 31st December 2008, 16:16

looks like ur going on a picnic! lol

**Sideways Sam** · 31st December 2008, 16:50

Originally Posted by dangerous

mine was at the bottom...

Damn, that's impressive. Who was it that said 4 strokes were boring????

I love blowing stuff up but that looks sort of expensive. I'll post a picture of mine when I get it to bits, that would require getting out of bed which I'm rather attached to at the moment.......

**TonyB** · 31st December 2008, 16:53

Dangerous, as the piston was cracked in half at the gudgeon, are you sure it didn't seize or something? IE the bike seized, piston cracked, then the rod broke? Just a thought.

**pete376403** · 31st December 2008, 16:54

Originally Posted by dangerous

mine was at the bottom...

Did you have to cut the piston in half to get the gudgeon pin out? That would indicate the pin had seized in the rod or piston. That could cause the rod to break. What provision do these motors have for pin oiling?

And shot peining (stress relief) is well worthwhile for rods. Kevin Cameron did this on the US kawasaki Superbikes to resolve rod beakage, until he was able to get titanium rods made (which may not be acceptable under your rules)

**Pumba** · 31st December 2008, 17:24

Originally Posted by busa pete

That's because your's is standard.

Yea I know, put gas in it and away I go.

**speedpro** · 31st December 2008, 21:54

Originally Posted by dangerous

mine was at the bottom...

I've broken a few 4-strokes, including turning one to shrapnell, and to me that looks like a typical piston failure happened. I've cracked Yoshimura and MTC pistons from the gudgeon pin up and across the crown. I always put the cause down as over revving. I've also sheared off the ring lands and ended up with a stack of washers - ring land ring land ring. Heaps of boost and resultant detonation was probable cause. Rods and bearings have never been a problem but I have never revved beyond calculated reasonable limits.

If you do the maths on the forces involved the horsepower being made adds so little extra force to the piston it really doesn't matter. Revs are the killer.

**Buckets4Me** · 1st January 2009, 08:35

Originally Posted by pete376403

until he was able to get titanium rods made (which may not be acceptable under your rules)

they are if you make them

but by the sounds of it it's the piston and rider at fault here
over reving the engine something most of us are at fault with
I know someone shifted wrong and bent some valves in his 100cc f5 bike at Taupo as well

**speedpro** · 1st January 2009, 09:22

"Technically", making an engine part for a bucket is against the rules. The rules state that the engine parts must be from a non-competition motorcycle. It doesn't actually say you can make them though modifying parts is OK. Noone cares though so it doesn't matter.

**dangerous** · 1st January 2009, 10:42

Originally Posted by speedpro

and to me that looks like a typical piston failure happened.

Yeah... at 1st I was thinking rod broke, but looking and thinking hard Im thinking the piston failed causing the rod to drop bashing a hole in the casing then snaping...
There is some odd marke on the piston were it broke almost like impurities in the casting.

Originally Posted by pete376403

Did you have to cut the piston in half to get the gudgeon pin out?

Na... the piston top was found at TDC the pin was on the crank... it was only the rings holding the 2 halfes to geather.