Nitrofisher

Hi, I have an Ofna Lx 1 and i was driving it last week until it just shut of. I opened up the motor and saw that the connecting rod had snapped andthere arelittle pieces all over in there. SoI was just wondering what would have caused this and also is this repairable and is so how do you repair it?

SyCo_VeNoM

they usually sell con-rods for the motor.

when you take the motor apart (like your rebuilding it, piston and sleeve have to come out) your going to have to clean it out well to make sure you get the busted pieces out so they won't score the piston head or shaft.


I had to replace a conrod in my HPI K4.6 cause the conrods bearing shattered and got ground up by the engine (sadly it ran its best after the rod broke)


From what I see the LX 1 uses a F.28 so a conrod shouldn't be a huge issue to find. I think the F4.6 conrod for a savage will fit (someone can correct me if I'm wrong) seeing they are the same engine manufacturer and engine sizes. its $22 on ebay buy it now if thats the case.

Nitrofisher

Thanx for all the info. I am new to this so I'm just wondering if theres anything special I have to use to clean it out?

jmaxey51

when taking the back plate off make sure the piston is up (closest to the glow plug) or when you pull the back plate off it will break the piston. i have seen people do it time and time again.

xxxtsuperstud18

why would it break the piston??? (this isnt me callin u a liar, this is me wantin to know for future reference)

Nitrofisher

This is probably a stupid question but where is the backplate?

jmaxey51

because the back plate has a groove cut out to let the piston go into. and if its down the piston is in that notch/groove and when you pull it off it will break, nitro engine pistons are so small/thin they will break easily.

Hoese37

The backplate is the rear cover. You want the pistom up because there is usually a notch in the backplate for the piston to go into when at the bottom of the stroke. Clean it out using Nitro cleaner, or denatured alcohal. remove the piston and sleeve from the motor and use a marker to reference which way the piston goes in the bore. Also note which way the oil hole in the rod is facing, usually faces towards the hole in the crank. Remove the carb and hold the engine with the back down above a clean rag and flush the bearings until clean. Feel by hand and check if there is ANY grittyness to the bearings, if there is grittyness to them, they need to be replaced. Install the new rod to the piston and reassemble, using either an after run oil, or 2 stroke engine oil. Be generous with the oil to the rear bearing, crank bore, and the piston pin and crank pin.

jmaxey51

its at the back of the crank case but you have a pull start or roto start plate. but still make sure the piston is up some pull start/roto start plates still have grooves/notches. i have had two engines with pull starts and one with rotostrart and only one of them you had to have the piston up but its better to go ahead and get into the habit now.

xxxtsuperstud18

ahh, makes sense. i have only took apart a traxxas 2.5. thats some good advice as i had NO idea that the piston needs to be a tdc to take the back plate off. when i get my +4 i'll have to remember that!!

jmaxey51

yea not all engines are made that way. i had a hyper 21 and SH 28 back plate that had a how section cut out so you didnt have to have it top of stroke but my v-spec, GRP, RB C-6, STS and Jammin JPX 21 all have to have it at top of stroke. and im pretty sure the +4 has to too. most race engines you have to do that. but alot of the RTRs, you do not have too but its good to go ahead and start doing it regardless if you have to or not.

Nitrofisher

I was also wondering if it matters if you touch the inside of the motor with your hands or with a rag?

jmaxey51

i would stay away from a rag just because some of the rags fuzz could fall into the engine and maybe mess something up. i just use rubber glove if i dont want to get my hands dirty but the inside of the engine seems to stay clean to the most part.

chookman46

Its also handy to remember to put the notch in the back plate at the top when you reasemble it too. Otherwise the piston will hit the back plate at bdc.

Also when a conrod breaks it can also damage the skirt on the bottom of the piston, so have good look at all the other parts in the engine before you go ordering a new rod.

The_Shark

you know, you might be better off getting a replacement budget engine, i dont like to fix things that catastrophically fail.

anyway, good luck if you rebuild, take your time.

bronx boy

xtm .021 is 59.00 on hobby people web site till monday picked one up as a spare it run as strong as my picco .021 and only stalled once during break in im really impressed with it