Broken Crank! Due to IRK

[Ry_Nos]

OK. so im sick of hearing about 'you cant put an irk on a non start in gear bike cos ul snap the crank'

Has anyone actually ever seen one? Simply due to the lightened fly wheel?

Ive had one on my Lifan 120 for ages. Its a non start in gear, has a hot cam too. Revs like all buggery. No Problems.

Im not after opinions, plenty of them around. I want actual happenings.

Cheers

 

[KTMKID]

good point man.... i dont see why you couldnt if you dont have any probs???

 

[sixeven]

I have seen many an auto clutch explode from IRK's and that would be more than 5. I haven't seen any manual clutch motors grenade from them but I'm making an educated guess when I say its because they don't have a bunch of weight throwing out whenyou snap the throttle. Thats what I know.

 

[tubes380]

i recently put a irk on my start in any gear bike but couldnt be bothered about lightening theoil slinger and all seems well for now.

 

[Power Man]

possibly, i thought i heard once , " good up to 10,000 revs" , whether that was on the crank or IRK" , but a inblalanced crank at high rpm could lead to that ?

 

[Ry_Nos]

Think about a standard engine. You have a flywheel on one side of the crank. On the other side you have the entire drive to the back wheels. It is already unbalanced.

I cant see how you can snap a crank simply due to an IRK.

 

[epod]

Anybody running 1 on start in neautral only bike.

Good point Ryan. I have one in my 138 with light oil sliger, but agree their is still a lot of weight on the clutch side anyway. I have another IRK but have not been game enough to install it on my Loncin 120cc( manual start only in neautral only). Is anybody running one on one of these.
Ride on

 

[Divy]

i just brought a irk for my lifan 138cc should i buy a lightened oil slinger ive heard yes to balance wieght an no no need
some one please answer as i have heard yes an no an i dont wanna fuck up my engine
thanks

 

[Big Air]

The Lifan 140s have alway been a crap motor if its not breaking crank shafts its breaking Kick starter gears and crankcases. All 14 crank shafts l have seen brake have been the same way the bike has lost spark and stopped most of the time, the flywheel has snapped off the stater senser as its spun around inside the stater cover. The crank shaft seems to brake in the same place each time, about 15mm of the broken crank is sticking out of the back of the loose flywheel. All the broken cranks l have seen have had standard outer rotor setups (flywheel) not one has had a inner rotor. l think Lifan make great motors but the 140 is not one of them its a dud why dont Lifan fix these serious common problems? YX 140 motors seem to be damn strong l work as a motorbike mechanic in melb vic.

 

[Cactus Jack]

You'd have to check what's left of the crank ends for run out with a dial indicator ... If the crank halves haven't been put together properly aligned , they'll run out and that'll put the flywheel out of balance ....

For the 15 broken engines you've seen , there are thousands more running around perfectly OK ... Lifan HAS improved the 140 ... it's called the 150 ...

It has to be remembered that horizontal engines were originally designed by Honda for low revving use in step thru bikes etc ....

Half of the problems stem from the fact that they're being advertised and sold as "Racing" motors ... so people who buy them TREAT them as "racing" motors ... Nowhere on the box or the Lifan website does it state that they are designed and built with racing in mind .... If you go flogging anything that's stock you'll have a good chance of blowing it up ... Engines that are intended for high performance use should be checked over and prepped ... that's just common sense ...

If you are going to go revving any engine to its max revs you should at least remove the flywheel and check the crank ends to see if they are running true ... And also get the balance factor checked out to see if it can handle high revs ...(like all decent racers or high performance engine builders do) ...

As to IRK's on non kick in gear motors ... I read on an Aussie Fast50's site which was advertising races and racing classes and rules where they stated that it was recommended to keep the peak revs below a certain point because the cast alloy clutch on the end of the crank can't handle the quicker rev up or higher revs which causes them to start spreading and going out of balance ... that in turn can cause the crank to fail ... If you run a billet clutch basket it should solve the problem ... but it's never a good idea to spin a clutch up to high crank shaft speeds on any motor .. car OR bike because they can fly apart suddenly ...