KX154 big bore stroker ride report! and Updates merged

[KawieKX125]

KX154 big bore stroker ride report!

All I can say is WOAHHHH!!!
The old engine I had was a fully built tom morgan engine straight from his team bikes and this thing absolutely smokes the old one, no doubt it was really fast as a 125 compared to what was/is offered in a kx, but the new engine is nuts. Tom claims the old engine dynoed at 38 hp when first built, and I always kept it fresh and this thing totally wastes it, it has to be over 40 hp, I am having it dynoed in a few weeks, I will let all know the results.

It has a 4mm bore, 4 mm stroke, minimal porting and head work, and I did it all for under 600 dollars (including the spare engine I used to build it from). This thing is seriously a cross between a 250 and a 125. Power of a 250 4 stroke (even more power) with the response and weight of a 125 2 stroke. Sounds pretty dang mean too. :aj: :cool: .

Gotta thank TNR for the awesome crank work (my buddy who assembles my cranks said it went together super easily), Eric for the case and head work, and my buddy for assembling the engine and getting me parts at his dealer cost.

Time to go riding!

 

[marcusgunby]

:yikes: :worship:

 

[elf]

Sounds like its really fast! Which is good news to me. My rod bearing just went bad on my 144 so I am going to have Eric stroke the crank and turn it into a 155. I was wondering how fast they were, I dont know anyone with one so your post is good news!!

 

[KawieKX125]

Go for it, its totally awesome, best mod ever.

 

[KawieKX125]

She siezed up today, IMS pro series rod appears to have fragged after an hour and taken out most of the motor with it, I am pissed. More to come.

 

[KawieKX125]

Need advice fast--

Just wondering where you all would go with this. As some might know, I just assembled a 154 stroker for my bike. I used all new bearings, new rod, etc. After 45 mins of ride time, the IMS rod snapped and destroyed cylinder, cases, piston, head, etc. All in all about 2000 retail in damage. The custom stroker crank is screwed up, custon cases gone, custom cylinder cooked. I am blaming a poor quality rod on the failure. The motor was professionally assembled, etc.

Would you guys bother to see if IMS will cover the damages or am I screwed because of the fact that it was in a motocross bike?

Thanks a bunch and I really appreceate any advice you can give. To add insult to injury, I go back to school in 3 weeks and now I cannot ride because my other 2 engines that I have are broken.

:bang: :bang:

 

[Chili]

Man Sorry to hear that :( You could try IMS but I'm guessing you'd need to prove to them there was a quality issue with the rod and not another issue that caused the rod to snap. Either way a bad deal all around.

 

[KawieKX125]

On a fun note, the destruction is the worst almost anyone I have showed it to has seen. It is pretty obvious it was the rods fault. Only other culprit could be hydrolocking, but the piston was at BDC when it happened so that really isnt possible (since the ports were uncovered).

 

[Rich Rohrich]

It is pretty obvious it was the rods fault. .

How exactly did you come to that conclusion?


You said it was professionally assembled. Did TNR assemble the crank or did your friend do it? If it was your friend what type of crank jig was used to assemble it?

 

[KawieKX125]

TNR didn't assemble the crank, but my friend who went to AMI and has rebuilt hundreds of cranks, and 6 for me did it. He does it the "old fashioned" way with no jig and trues it after it is assembled with two v blocks and dial indicators. THen we use the suzuki style puller tool to install them.
Rich, if there is something else that would cause a rod to snap so suddenly, please enlighten me. I have grown up alot since my days when I used to spend lots of time here and I don't want this to turn into one of your "I know everything and you are wrong and you jumped to a conclusion what the heck were you thinking" threads.

But back to the crank, the runout was nearly zero, sideclearance was exactly in between kawasaki's recommended range. Crank was centered using feeler gauges (I believe we used a .015" to start with). Moose crank bearings were used. I do a rod and crank bearings in this motor 2x per year and have never had a problem (usually use hot rods). Not untill I switch rod brands, do I have a problem.

I think it is pretty obviously the rod because the bike was not vibrating at all and it was running perfectly up untill the instant it fragged (which thankfully happened as I landed and not in the air or takeoff). The rod is also broken clean off, except for the half which whpped around and took out the remainder of all the parts that were still good. The lower half of the rod had so much force, it sliced a notch straight up through the piston and cylinder, then came back down, made a revolution, and jammed itself through the front of the case and water jacket (that would explain all the water in the cases when I took it apart).

At first I thought it had hydrolocked, which I have seen in jet skis and causes similar damage, but for it to hydrolock, something would have had to been severely blown and very quickly filled the cylinder with water. There is no evidence of either head or base gaskets leaking, and once again, I think I would have noticed earlier that there was water in the motor, last time I had a leaky head gasket, the bike ran like crap.


But, I since the head is good enough to use, trans is fine, crank halves are most likely okay other than some cosmetic damage and all I really need is cases, cylinder, rod and piston, I can get it back together fairly cheaply. I have cases, and I am sure eric has some sort of cylinder. The rod is easy enough. I just want to know why it failed if it wasn't the rods fault so it wont happen again.

 

[Vic]

I'm no expert, but I did stay at a Holiday Inn Express last night.

Sounds like the rod is defective.

 

[Rich Rohrich]

The rod is also broken clean off,

Where did it break exactly? Where a rod breaks can usually give you some idea as to why.

 

[KawieKX125]

Here are some pics, your advice is greatly appreceated, I know you are just about the best person to ask this to-

http://www-personal.engin.umich.edu/~aslids/bike damage/

Gotta love what the rod did to the cylinder and piston, THEN what it still had enough energy to do to the case. The rod has parts that are mushed over, but that is from smashing into other parts as it spun. The part that is still attached to the piston (As you may or may not be able to tell from the pics) is for the most part cleanly broken off as if it was put in a shearing machine.

 

[Rich Rohrich]

Is there any evidence of piston to crank journal contact, or any evidence of the piston and head making contact prior to the rod breaking? I know that might be tough to determine but it's worth looking at.

What does the metal at the break look like? Is it a consistent grain and coloring? Do you see any voids in the top piece that don't have a matching fill on bottom section of the rod, or vice versa?

 

[KawieKX125]

There are tiny tiny voids. I will send all the parts to you and eric if you want for you to analyze. There is no evidence of contact and the engine was perfect, and I mean perfect, quiet (except for powervalve noise) and ran extremely well. It was running extremely well up untill the instant of the bang and immedeate seizure.

What are your initial thoughts about it?

Also, what about moving this to mods and performance forum since this is now turning into a technical thread?

 

[Rich Rohrich]

What are your initial thoughts about it?

Based on what you said and where it broke, it certainly sounds like it could have be a manufacturing flaw. That's a pretty weird place for a failure in a normal running engine, especially considering the short time on it.

I'd call IMS and offer to send it to them. Good companies try and take full advantage of failure analysis opportunities when they present themselves, especially in the case a 1 hour failure. If you present your case to them logically and most important of all without emotion you might get somewhere with them.

 

[KawieKX125]

Ill see what they say. If they don't want it, do you and eric want it to analyze.

 

[Rich Rohrich]

Ill see what they say. If they don't want it, do you and eric want it to analyze.

Sure, if they don't want to see it I certainly would.

 

[KawieKX125]

Sounds good, I will call IMS then Eric (I assume he can get it to you) tomorrow. On that note, tell him to send the big wheel engine out sometime soon!!! He has had it for 2 months now :) .

Could it have broken from being free revved in the air. I usually goose the throttle right before I land and it seemed like the second I landed from this jump, it made the bang and siezed. Everyone at the track said the bike sounded fine untill it went bang (while was realllllly loud). What about it being a stroker big bore engine? Could that have that much extra stress on the rod to make it break that suddenly?

 

[jaguar]

the price of big power

 

[steve125]

She siezed up today, IMS pro series rod appears to have fragged after an hour and taken out most of the motor with it, I am pissed. More to come.

:ohmy:

 

[Rich Rohrich]

Sounds good, I will call IMS then Eric (I assume he can get it to you) tomorrow. On that note, tell him to send the big wheel engine out sometime soon!!! He has had it for 2 months now :) .

He was working on it on Saturday.

Could it have broken from being free revved in the air. I usually goose the throttle right before I land and it seemed like the second I landed from this jump, it made the bang and siezed.

If you think about it, a no load situation is when rods are most likely to break. High cylinder pressure works as a compressive load on the piston to cushion the stress on the rod as it slows down at TDC. It's sort of like an airbag for the rod. When there is less load and less pressure on the piston crown but the rod is subjected to high rpm, you get a high stress stop at TDC then the rod is yanked back down . Without that pressure on the piston the piston continues to want to move up as the rod is pulling it back back down and effectively stretching the rod. Add in a heavier piston and an the increase in stress it produces near TDC and you can see how the rod could snap like silly putty being stretched beyond it's elastic limits. For the same reasons four-strokes tend to break their rods as the throttle is being closed after running at high speed.

Usually this only tends to be an issue after a lot of cycles on the rod, but if you get the right set of circumstances together, and you have a rod that maybe isn't as elastic as it should be I can see where it might SNAP. :yikes:

There is a good reason why the study of metal fatigue and materials science is such a specialized engineering discipline. There is a whole lot going on inside the engine that rarely gets considered.

 

[viking20]

I really feel your pain.......Our cr 125 did the same a couple of years ago , damaging about the same parts....Thanks to some extremely helpfull people in here it didnt get as expensive as it could have been ( Guys , you know who you are , I will never forget it ! )
Really , really sorry for you , just looking at the pics makes me sick.....
Positive : great info , Rich ! A couple of things there ( again !) that I never thought about....
Kawie , I hope you get things sorted as cheap as possible , and please let us know when theres any news.....

 

[steve125]

Kawie, can you show us some pics of the piston top and head? Also did you check your squish clearance during your build? If so what was it?

If no piston contact was made with the head or crank prior to the rod failure. Then IMO it looks like there was a defect in the rod.

Also did you notice any sounds of "pinging", at any time when running this engine??

Rich, looks like the rod snaped after TDC???

 

[elf]

Go for it, its totally awesome, best mod ever.

Still think I should go for it? :think:

Thats some brutal damage! Hopefuly its the rod and not something you did. I have heard of weisco paying to fix some guys bikes due to product failure so maybe IMS will do the same. Still a lot of work for ya and you dont get to ride so that sucks.