2 rod failures, synthetic oil the cause?

Dave_In_Florida

Dave_In_Florida

New Member
#1
#1
Do any of you guys have issues running lighter weight oil on your motors? My friend and I are both running 5-30 synthetic (Royal Purple) and both had rod failures today drag racing.

My motor is a brand new clone, his is a real honda that we pulled apart and it looked fine inside. Both locked the rod to the crank. The only thing we did is remove the governor and put springs and 4 degree keys in. Revs were way below 6000 on both motors.

I just can't imagine what I could've done to hurt both motors in the same way. I used an impact to put the flywheels back on, but since that won't set end play, I can't imagine that hurting anything. We're both stumped and bummed
 
J

jareeb

New Member
#3
#3
Dave_In_Florida said:
Do any of you guys have issues running lighter weight oil on your motors? My friend and I are both running 5-30 synthetic (Royal Purple) and both had rod failures today drag racing.

My motor is a brand new clone, his is a real honda that we pulled apart and it looked fine inside. Both locked the rod to the crank. The only thing we did is remove the governor and put springs and 4 degree keys in. Revs were way below 6000 on both motors.

I just can't imagine what I could've done to hurt both motors in the same way. I used an impact to put the flywheels back on, but since that won't set end play, I can't imagine that hurting anything. We're both stumped and bummed
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Did you break the engine in on that oil?
 
jprice

jprice

OldMiniBikes.com
#4
#4
i would say so dave,
my buddy ran a stock clone rod in his for months and he had a worked up head,bigger cam and bored carb,and was spinning past 6000 for sure! the rod did end up going on him but it never siezed to the crank, i think the rod bolts ended up stretching...
and i really wouldn't use a impact gun to tightin the flywheel you may be asking for more trouble ....
the good news is ombwharehouse should have the crank which is cheap enough, and they have the arc rod, order today and you will be racing saturday lol

BSP Clone GX200 Stock Crankshaft - DJ-1275

Billet Rod 3.323 Honda GX200 +.020
 
graygoose420

graygoose420

New Member
#5
#5
Tear it down and see if the bearing Is fried . If so the oil couldn't protect and lube anymore . my guess would then be the oil was too thin or was cheap.
I run amsoil full synthetic 10/30 . Never had a problem . Even with a stock rod. My motor turns 8200/ 8500 almost every weekend . It's been running since the Feb. Of this year.
Hopefully nothing broke in there . Buy the billet parts its worth it.
 
minibikin'

minibikin'

Sho-nuff
#9
#9
Royal purple is know for hp increases but premature failures. I have no experience, just reading on Yellow Bullet and mustang boards. Im not an expert or a scientist. Mobil 1 synthetic 10/30 for me.

Sent from my DROIDX using Tapatalk
 
J

jareeb

New Member
#14
#14
arnt you not suppose to break an engine in on synthetic oils? but then once its broken in you can switch to them, its just what i have heard never ran syntheic oils before and dont need to at the moment.
 
Dave_In_Florida

Dave_In_Florida

New Member
#15
#15
MB165 said:
What do the bearing journals and crankpin look like?
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I haven't pulled mine apart, but on the Honda, it looked like contaminants in the oil honestly. There were grooves in the rod, and deposits of aluminum on the rod (high spots) and the crank. The thing is there was nothing that should have contaminated it, it was clean inside.

My friend and I thought it might be oil related, because that's basically what the two motors have in common, but I don't want to jump to conclusions.
 
Dave_In_Florida

Dave_In_Florida

New Member
#16
#16
jareeb said:
arnt you not suppose to break an engine in on synthetic oils? but then once its broken in you can switch to them, its just what i have heard never ran syntheic oils before and dont need to at the moment.
Click to expand...
This is the first performance small engine I've done, but I've built a few high performance car engines in the past. I personally don't believe in breaking motors in (speaking of those with roller cams here). I just fire it up and do what I want to do with it. Maybe because these motors don't have a true rod bearing a break-in is more important? :shrug:
 
graygoose420

graygoose420

New Member
#17
#17
Dave_In_Florida said:
I haven't pulled mine apart, but on the Honda, it looked like contaminants in the oil honestly. There were grooves in the rod, and deposits of aluminum on the rod (high spots) and the crank. The thing is there was nothing that should have contaminated it, it was clean inside.

My friend and I thought it might be oil related, because that's basically what the two motors have in common, but I don't want to jump to conclusions.
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I strongly belive it was your oil.
Either two things happend - bad oil choice, or you might have over tightened the rod . Just my opinion.
post pics of the bearing.
 
Dave_In_Florida

Dave_In_Florida

New Member
#20
#20
I found a thread on a kart racing forum where a guy had the exact same thing happen on a 6.5 blue clone in a race kart. The general consensus is it's a common issue on the blue motors due to tight clearances from the factory, and is exacerbated by my lack of a break-in period.

I'll probably use this as a chance to upgrade and put an ARC rod in it, and probably get the crank polished to try to get it round and back into shape. I'll also use this as a learning experience to break these motors in on dinosaur oil before running the synthetic stuff.

Greg, it was still awesome to meet you and your family, and we'll definitely get together and ride soon.
 
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