FXR150 conrods breaking

[Sideways Sam]

We just broke a conrod on our bike, put a hole right through the crankcase. One day later Dangerous did the same thing to his engine. This is the third conrod break I know of on one of these engines in the last month or so. I've also heard of a lot of others through the grapevine.

It would appear that this is a weak point in these engines so I'd like to hear from anybody else that has had a similar incident. We had increased the compression on our bike which wouldn't have helped but the rod lasted less than an hour!!!!!

If anybody who has had a similar problem could post details, particularly:
Compression Ratio
What engine was doing at time of failure (revs etc)
other mods

I realise that most of you won't want to admit to your mods in case somebody copies them but the truth is most of the races I've seen are currently being won by stock engines........ These things are breaking regularly and it would be in everybodiy's best interests to find the source of the problem so that we can build reliable engines (I'm currently looking into getting Wiseco to make a batch of rods for these things)

I'd also be interested to hear from anybody regarding seizures and the circumstances surrounding them.

[Kickaha]

(I'm currently looking into getting Wiseco to make a batch of rods for these things).

Why not use stock rods and get them shot peened

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

[bucketracer]

You Guys should give up on those fussy, fragile, heavy, difficult to maintain, expensive, performance limited, technically complicated 4 smokes and go with one of those strong reliable, light, quick, easy to work on 2 strokes that have loads of performance potential.

[Pumba]

Bugger, wasnt such a good Taupo then.

Ive had no issues, but I will be watching with interest.

[Mrs Busa Pete]

Bugger, wasnt such a good Taupo then.

Ive had no issues, but I will be watching with interest.

That's because your's is standard.

[Sideways Sam]

Why not use stock rods and get them shot peened

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

Damn fine idea, I'd already thought of shot peening, I'm not sure it's going to make the difference we need though.

The mods I had made to my engine were turning out an estimated 35% increase which is a lot more stress on everything. Some of the bike that are dropping rods are stock standard.....

Does anybody know how much shot peening can do to stregthen a rod?

[Sideways Sam]

Bugger, wasnt such a good Taupo then.

Ive had no issues, but I will be watching with interest.

Taupo was great, would've been a hell of a lot better if we had a bike that went though!!!!

Spent the time on the recover vehicle peeling bikes off the track and sweeping up oil......... Bloody classics..........

[Sideways Sam]

You Guys should give up on those fussy, fragile, heavy, difficult to maintain, expensive, performance limited, technically complicated 4 smokes and go with one of those strong reliable, light, quick, easy to work on 2 strokes that have loads of performance potential.

I've only got one thing to say to that:

It's been a long time since I saw a 2 stroke win anything in F4..... I'm sure there is a lot of potential for it to happen but I haven't seen it for a long time. Rob was going really well at Taupo but still a long way behind Rick and Dave on their FXRs. If Rob could have held more corner speed he might have been in with a chance, I know I can't catch him on a straight section.

[Buckets4Me]

W(I'm currently looking into getting Wiseco to make a batch of rods for these things)

not in the rules is it
I wasnt allowed to use Bousen reeds

got to be a stock rod as I have been told by the welly crew
or its not in the spirit or rules

[Buckets4Me]

I've only got one thing to say to that:

It's been a long time since I saw a 2 stroke win anything in F4..... I'm sure there is a lot of potential for it to happen but I haven't seen it for a long time. Rob was going really well at Taupo but still a long way behind Rick and Dave on their FXRs. If Rob could have held more corner speed he might have been in with a chance, I know I can't catch him on a straight section.

the number 1 plate is on a 2 stroke that broke on saturday and would have won easily like it did last year

it's all in the rider and bike
plus the 4 strokers need more cc's to compeat and they dont get the handycaps the 2 strokers get

[Sideways Sam]

not in the rules is it
I wasnt allowed to use Bousen reeds

got to be a stock rod as I have been told by the welly crew
or its not in the spirit or rules

It's a mute point in the rules

"Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the make, type or design of carburettor, ignition, exhaust, piston, cam, valve
springs or cooling system except for class eligibility."

It depends if it's classified as a transmission part or not. As far as I'm aware the rods being sold on www.fxr150.co.nz are competition rods and therefore that would mean a large portion of the bikes out there wouldn't qualify, especially in the South Island. I'm sure that JC's 125 twins (the fast ones anyway) aren't running stock rods etc.......

If it's OK to change the piston, surely it's OK to change the rod?

This will be an interesting discussion!!!!!!

[Sideways Sam]

I've just had confirmation from a guy that's done 2 big ends:

One was due to a gudgeon pin clip getting loose and making it downhill to get in the way of the big end

The other was probably stuffed before he bought the bike

[Kickaha]

As far as I'm aware the rods being sold on www.fxr150.co.nz are competition rods and therefore that would mean a large portion of the bikes out there wouldn't qualify, especially in the South Island. I

The rod I got from them was a Suzuki rod, there's nothing special about them

[Buckets4Me]

It's a mute point in the rules

"Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the make, type or design of carburettor, ignition, exhaust, piston, cam, valve
springs or cooling system except for class eligibility."

It depends if it's classified as a transmission part or not. As far as I'm aware the rods being sold on www.fxr150.co.nz are competition rods and therefore that would mean a large portion of the bikes out there wouldn't qualify, especially in the South Island. I'm sure that JC's 125 twins (the fast ones anyway) aren't running stock rods etc.......

If it's OK to change the piston, surely it's OK to change the rod?

This will be an interesting discussion!!!!!!

I hadn't thought about the rods on that fxr150 site good point I'm putting a protest in now
we will ban them dam fxr's 1 way or another

na I dont realy care and i say it's an aftermarket part not a race part lol
it's a road bike after all not a race bike like the cbr150's
no one other than buckets race them

[TZ350]

I've only got one thing to say to that:

It's been a long time since I saw a 2 stroke win anything in F4..... I'm sure there is a lot of potential for it to happen but I haven't seen it for a long time. Rob was going really well at Taupo but still a long way behind Rick and Dave on their FXRs. If Rob could have held more corner speed he might have been in with a chance, I know I can't catch him on a straight section.

Its been a long time since a 4 stroke won a F4 GP so 4 stroke riders should cherish last Saturday, it might not happen again for a while.

The fact a Grey haired old man could threaten the cream of the 4 stroke world should give every one pause for thought. He has finished more races than most and headed Tim (FXR 150) the eventuall winner for most of the last race.

A quick look through the Mt Wellington results shows all 4 strokes in the top positions except for the GP's.

.