Husaburg 570fe

[NVRENUF]

The turbo is on a 2013 KTM 450 done to the 520.
Thanks for the KMS info, The under pipe works good and cleans it up a lot, makes easier to work on.

I agree with too much RPM for a long rod motor, long rods usually are low RPM things that make torque, going back to my race car V8 days. And twin cams much better to rev too.. yup.

The experiments continue.

 

[M5-]

When I had my 520 built last fall a brand new KTM rod went into motor at that time. I never really kept track but I'm guessing I had 60ish hours on the motor and the new rod let go, KTM said get fawked you're on your own. This is on a non turbo motor. I'm thinking the 4Ts just can't take the extended rpm of a snow bike pull. I rode my bike quite a bit harder this last season, my second, as compared to my first season. I just received the rebuilt rebuilt engine back so I'll run it this summer and see how it goes. I don't know what the answer is but it's expensive to blow up one of these motors that much I do know.

M5

 

[NVRENUF]

That sounds strange. What year is that bike? We built a few 520's on new 450's last year, not one failure. Why did you get a new rod with the 520 kit?
Who's piston is it? Do you know the compression ratio? Was the piston weight comparable to stock? Not sure why the rod let go.

The 520 kits we have built were cp pistons from Carillo. 12:5 to 1. Just a resleve of the stock 450 jug, and stock rod. We had a few naturally aspirated ones, and a few turbo ones.

I was thinking of getting a carillo rod and welded crank for my 520 just as insurance to have a good winter. It's $1800 for the crank complete, but cheaper than a rebuild and no time wasted.

 

[M5-]

The motor is a carbed XC4. The work was done by Thumper Racing in Nevada. I had a lot of hours on the stock motor so it was due. Last fall I reached the turning point on the bike, either throw some money at it or blow it out. I decided to redo the motor. I would have done it myself but when I looked at the lost wages from working vs having it done it was cheaper to have it done. Not sure how familiar you are with the XC4 but I had everything updated, single sump conversion, updated new rockers, oil jet, new oil pump gears, valve job, crank rebuilt, the works. The motor had 400 hours on it including 1 season of snow biking so the old rod was out of spec and was replaced when the crank was rebuilt. I'm not sure what the CR is now or who supplies TR's piston, I thought it was Wiseco but I honestly can't remember. As a 520 the bike was noticeably better on the snow, I never rode it on the dirt but I will this summer. I'm starting to think big torque at low rpms is the answer for longevity which is why your 660 might be the ticket.

M5

 

[tillbuilt]

I got my piston for my Berg 450/520 from thumper racing and it was a CP.