# 2005 BF 750 motor locked up?



## JJB (Feb 5, 2010)

All stock, 400 hrs, runs strong no issues. Rode two weekends ago for several hours. Started up today idled for 5 mins, took off easy and at about 5 mph something internal started knocking and banging loud. Sounded nasty. Shut it down now motor will not turn over. Starter and battery are strong. Any ideas or things to check besides pull motor? Timing chain? Thanks


----------



## Hotbrute750 (Sep 24, 2009)

Check your oil level.. Just something to look at.. if it sounded that nasty doesnt sound good to me. Good luck. I think you know you just dont want to admit it.. lol


----------



## brute for mud (Jul 15, 2010)

if i remember right you should have a recoil try and pull it over and see if it spins over if not time to pull it apart


----------



## JJB (Feb 5, 2010)

Oil level is 3/4 on the band. It doesn't use a drop of oil. 

I pulled the rope gingerly...no go. It's locked. Will attempt to spin it in reverse tomorrow using the primary.

After searching old threads I think it threw or broke a timing or oil chain. I don't think a rod or crank bearing would make the kind of snap, crackle, and pop that I heard. Seems to be an awful lot of 05 and 06's with this problem. 

Makes me want to puke. This quad is babied and does not go near mud or deep water. Serviced and maintained properly. Idles for 10 mins before it ever goes in gear. Driven for 10 mins and warm before it ever sees a heavy throttle and now this.

Why is there nothing in the maintenance schedule to check and/or replace these chains at some frequency?


----------



## Roboquad (Sep 8, 2009)

I have an 06...know the pain. Pull the cam caps to check the chains. A bore scope would speed things up.if not. You just got to dig in till you find it. Good luck.


----------



## JJB (Feb 5, 2010)

Does this seem to be an OE chain problem, ie, are replacement chains better? Or is it something about the 05-06 motor design?


----------



## LM83 (Jul 23, 2010)

I don't think your suppose to let a brute idle that long. I've heard if they idle 5mins+ that there becomes some oil pressure issues. I think it even says it in the handbook.


----------



## NMKawierider (Apr 11, 2009)

LM83 said:


> I don't think your suppose to let a brute idle that long. I've heard if they idle 5mins+ that there becomes some oil pressure issues. I think it even says it in the handbook.


Yeah I don't think its good to idle any engine for long periods...and i dought most Brute owners ever realy warm theirs up before lett'n em graze...I know I don't..maybe two minutes if its lucky.


----------



## LM83 (Jul 23, 2010)

nmkawierider said:


> Yeah I don't think its good to idle any engine for long periods...and i dought most Brute owners ever realy warm theirs up before lett'n em graze...I know I don't..maybe two minutes if its lucky.


 I try to give mine a couple of mins, followed by some low rpm cruising. Like I said, I remember reading in the handbook where its not suggested to let the brute idle for more than 5 mins. 5 mins is a long time if you think about it too.


----------



## JJB (Feb 5, 2010)

So engines sieze because they idle too long? 10 mins vs 5 mins? I don't buy it. Isn't there a oil pressure monitor and warning light? Wouldn't that come on during these dangerous idle periods? 

Working an engine hard before it is fully warmed to operating temp is not a good thing IMO.

Edit: just located the extended idle warning. The danger it's referring to is overheating. Obviously not an issue when the bike is cold (as in been sitting for days or weeks). That's the 10 min warmup time I was referring to...cold startup...not after the engine is warm.


----------



## LM83 (Jul 23, 2010)

JJB said:


> So engines sieze because they idle too long? 10 mins vs 5 mins? I don't buy it. Isn't there a oil pressure monitor and warning light? Wouldn't that come on during these dangerous idle periods?
> 
> Working an engine hard before it is fully warmed to operating temp is not a good thing IMO.


 I'm just telling you what I remember reading in my handbook. I agree with you on working a cold engine. Thats why I do around 10mins or so of low rpm cruising before I put her to work. Not even saying the reason your engine seized is because of letting it sit and idle. Parts wear out. Simple as that. 3/4 the way up the dip stick isn't good on a brute either, it needs to be FULL of oil at all times. I've read horror stories of brutes that ran 3/4 or so on oil. Well from my experience on my brute, when my oil light came on last year I shut it down right then, didn't matter. It was to late. Light was on maybe 5 seconds.


----------



## LM83 (Jul 23, 2010)

Ah see I didnt know you were saying cold startup.


----------



## NMKawierider (Apr 11, 2009)

Keeping in mind too that engines get lubercation several ways. 1. by direct pressure or supply from the pump like the crank and a few other things straight off galleys. 2. by spray or slinging off other rotating parts like crank throughs up to the cylinders and gears slinging to shaft bearings and 3. by return streams of oil on its way back to the sump.. like cam chains ...and other chains.

I just have to believe with long periods of low rpms... at least some parts won't be as well supplied..or lubed.. as they would be at higher rpms. 

Did ideling kill your engine? No, probably just had some bad part what's time was up at about 400 hours. I think we all would like to know what actualy did happen though and why.


----------



## Roboquad (Sep 8, 2009)

Did you pull the covers to check for broken chains??? I think OE. is the only way to go, Ive never broken or stretched a chain and rode my bike hard enough to melt the cam holders into an aluminum wave.warped both heads and the front jug......guess you're just lucky..:bigok:wonder if the oil pump malfunctioned? see if you have fresh oil on the cam. Just throwing out idea's... the tensioners are cheap plastic. could have broken one, letting the chain jump.


----------



## MeanGreenMan (May 24, 2010)

Any finding yet, rod bearing seizure (I bet on this) or broken chain?
Drain the engine oil and see what's in it.


----------



## JJB (Feb 5, 2010)

No time to look at it yet. Hope to get some answers this week. Can someone point me towards rebuild options? Maybe I'lls start a new thread.


----------



## JJB (Feb 5, 2010)

MeanGreenMan said:


> Any finding yet, rod bearing seizure (I bet on this) or broken chain?
> Drain the engine oil and see what's in it.


Just curious...why do you think it's a rod bearing?


----------



## brute for mud (Jul 15, 2010)

brutes are known to spin rod bearings 1 if you swamp it 2 if low on oil


----------



## Moneypit (Dec 11, 2010)

Sounds to me like it either broke a chain or the chains were stretched to the point where a piston took out a couple of valves. The engine won't be able to crank if you have broken valves sitting on top of them. Rod bearings would also be a possibility, but unless it threw a rod the crank could still make complete rotations, it would just be really noisy. Good luck with it.


----------

