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PostPosted: Thu Jun 29, 2017 1:54 pm 
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DR650 Limits Tester
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Joined: Tue Sep 11, 2012 10:04 am
Posts: 1915
Location: Summerfield NC
Any BBF experts out there, i figured this is a odd ball question for the DR community, but im stumped.........

My Donzi has a 460 big block ford motor in it, 20hrs on rebuild, pretty much stock just big holley carb, edlebrock cam and intake, HEI distributor. Yesterday i launched the boat, started it up and got it to operating temp, brought it up to full speed for about 10 seconds and backed off as i came in to the no wake zone and was smooth as could be, until about 20 seconds after it started to knock, to me standing above the motor it clearly sounds like a rod. so i shut it off for about 30 min, fire it back up and its gone.....completely, rev it ut, hold 3k rmps for a minute or so, bring it back down to idle and its silent for 30 seconds........then the knock re appears :s_dunno . so i crawled down in to the engine compartment and what initially sounded like a rod knock sounded to be coming from the middle to upper end of the engine once i got down in there again i have no idea :s_dunno . so i figured its got oil, it got tons of oil pressure, and its not over heating, so i took it out for 2 hours and ran it half to wide open throttle the whole time and not a sound until i dropped it down below 2k rmps or so. now the only issue i have had with it so far is a little hesitation off idle, and in intermittent miss at cruise speed that cleared up around half to 3/4's throttle and above. and to me the oddest thing of all is it never got any worse.

im stumped really, i dont know big blocks im a german car, motorcycle and two smoke jet ski engine guy. is it a rod? is it a lifter? bent push rod? what to check, what to do?

if anyone has any suggestions, recommendations or can point me to a good Big Block Ford expert i would greatly appreciate it.

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Brandon,
2006 DR650 Race Bike: FMF power bomb header, FMF power core 4, DDC and Race Tech springs, Cogent Mojave Pro Series, Ohllins spring, Pro taper bars, Clarke 3.7 tank, Seat Concepts seat, air box mod, Twin air filter, sumo fender, Acme Zoom panniers, off road gearing, Warp 9 Gold hubs and Black wheels, 320MM big brake kit, TM40 Carb, Mad Man Engineering built head, decked cylinder, engine assembled and tuned by VAR.

03 sprinter motobus
Donzi Z-25


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PostPosted: Thu Jun 29, 2017 2:33 pm 
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Adventure Rider
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Joined: Sat Mar 17, 2012 5:31 pm
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Location: Central Florida, Where the clueless go to drive...
Just guessing, distributor/oilpump drive? Cam chain issues? Cam bearings?

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Spaced Coast, FL
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PostPosted: Thu Jun 29, 2017 3:03 pm 
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Single Tracker
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Location: Southern WV
I'd get a hose or something to use like a stethoscope and try and pinpoint exactly where the knock is coming from. Its possible it could even be the outdrive and not the engine.

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PostPosted: Thu Jun 29, 2017 4:26 pm 
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Trail Rider
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I think you are on the right track thinking valve train; lifter or pushrod maybe rocker nut misadjusted or backing out.


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PostPosted: Thu Jun 29, 2017 9:56 pm 
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Single Tracker
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Location: Biloxi, Mississippi
Flat tappet cam? These require proper break-in unlike a roller tappet camshaft. A lifter will knock/tap when a loss of oil to that lifter occurs. Reason being is the lifter has a loss of oil pressure causing slack in that lifter pushrod assembly. Also could be a loose rocker arm. This will cause tapping and a bit of hesitation upon off idle acceleration like a burned exhaust valve would, then clear up. Pull the valve covers off and check each individual rocker arm assembly... I'm sure you will find a loose one. Start at TDC on cylinder #1 and rotate the crank and go from there. Hopefully not a bad lifter as this will require the removal of the intake to get at. If it is a roller cam motor, the head would have to be removed to replace the bad lifter as they are much taller than the flat tappet lifter....Hope this helps... I am a ford guy, although with small block Windsor experience.


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PostPosted: Fri Jun 30, 2017 9:34 am 
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MSF Student
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Joined: Fri Dec 16, 2016 9:19 am
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Location: Central FL
Can't help from here. I am also keeping an old OMC stern drive drive running. It get's interesting when you need certain parts but she keeps on working.


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PostPosted: Fri Jun 30, 2017 10:20 am 
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SuperMoto Dude
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Joined: Wed Apr 06, 2016 4:27 pm
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Location: Ventura, CA
I'm with Mattbowdeen.. it's exactly what I was thinking.


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PostPosted: Fri Jun 30, 2017 2:03 pm 
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DR650 Limits Tester
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Joined: Tue Sep 11, 2012 10:04 am
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Location: Summerfield NC
i guess a large part of the problem is i dont know the specifics of this motor........no clue what cam, no clue what pistons, literally going off the PO's word.



so i think i have found my answer

a fresh 532 stroker motor :idea: , that way ill have another 150hp, the boats value goes up, and i know what i got :BevButt: .

the more i listen to it i believe it to be a rod unfortunately and i read these motors in marine applications had some lubrication issues. As much as i dont want to fork out the cash for a fresh motor id rather know what i have and be confident its not going to let go on me.

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Brandon,
2006 DR650 Race Bike: FMF power bomb header, FMF power core 4, DDC and Race Tech springs, Cogent Mojave Pro Series, Ohllins spring, Pro taper bars, Clarke 3.7 tank, Seat Concepts seat, air box mod, Twin air filter, sumo fender, Acme Zoom panniers, off road gearing, Warp 9 Gold hubs and Black wheels, 320MM big brake kit, TM40 Carb, Mad Man Engineering built head, decked cylinder, engine assembled and tuned by VAR.

03 sprinter motobus
Donzi Z-25


Last edited by crash on Thu Aug 03, 2017 1:54 pm, edited 1 time in total.

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PostPosted: Thu Aug 03, 2017 11:08 am 
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DR650 Limits Tester
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Joined: Tue Sep 11, 2012 10:04 am
Posts: 1915
Location: Summerfield NC
ok, so i found my issue. :s_bomb


so for the longest time (45hrs of run time) i could not figure out that noise, i wasn't consistent, it went away at higher RPMS, and the dam thing ran great............well fast forward to this past sunday. fired the boat up, took her out ran it for 20 min, shut it down sat for a few, fired it back up, and it idled smooth for about 15 seconds and the rod let go and what a noise she made lol.

so luckily i had bought my new BBF532 stroker with aluminum heads last week, which delivered today, but i am still short one part.........the cam and that is because i cannot for the life of me figure out to go with a roller cam or a flat tappet cam. anyone have any experience here with performance marine engines, I've heard horror stories on roller lifters failing, and horror stories of flat tappet cams failing and cant decide which way to go. im looking for reliability and longevity over extra power at this point. if anyone has any experience here i would greatly appreciate the advice.


thanks

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Brandon,
2006 DR650 Race Bike: FMF power bomb header, FMF power core 4, DDC and Race Tech springs, Cogent Mojave Pro Series, Ohllins spring, Pro taper bars, Clarke 3.7 tank, Seat Concepts seat, air box mod, Twin air filter, sumo fender, Acme Zoom panniers, off road gearing, Warp 9 Gold hubs and Black wheels, 320MM big brake kit, TM40 Carb, Mad Man Engineering built head, decked cylinder, engine assembled and tuned by VAR.

03 sprinter motobus
Donzi Z-25


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PostPosted: Thu Aug 03, 2017 12:45 pm 
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Adventure Rider
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Mongle, over in the ADVrider DR650 thread does marine engines for a living. I'll have him take a look at this thread. :s_yes

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