Author Topic: general cost to rebuild a motor. (Read 15971 times)

cafe2be · « **on:** January 25, 2009, 04:43:33 PM »

Just a random questions. My motor does not need a rebuild. Just figured it would be something to look into while the motor is out. So from Soup to nuts what would it cost.
I have the gasket set.
The motor in question is a 77 750f

mrbreeze · « **Reply #1 on:** January 25, 2009, 04:47:08 PM »

How can you generalize? You don't know what you will find when you open it up.Also depends what you want to do to put it back together.

crazypj · « **Reply #2 on:** January 25, 2009, 04:50:10 PM »

Plan on at least 8~10 hrs labor plus parts for a full strip/clean/re-assembly
PJ

NitroHunter · « **Reply #3 on:** January 25, 2009, 05:04:09 PM »

Quote from: cafe2be on January 25, 2009, 04:43:33 PM

My motor does not need a rebuild.

At this point, zero $$

Give us an idea of what YOUR theoretical 'rebuild' would en tale, such as new rings and a valve job or the full monte? Left to our own devices, we could get you into double jeopardy in a flash.

"I'll take stroked-turbo-gold plated-billet for $25,000, Alex".

WFO · « **Reply #4 on:** January 25, 2009, 05:07:57 PM »

Don't forget to factor in 2 cases of beer, most folks overlook that expense.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #5 on:** January 25, 2009, 05:19:54 PM »

If it doesn't need a rebuild but your curiosity gets the best of you, you're out your gasket set. F2/F3's are notorious for bad valve guides. Head work can get expensive. I'd say minimum for guides and seals done $500. Ask MRieck. Valves, springs, retainers maybe. Porting. A good head job could cost more than your bike is worth. Rings and honing. Couple bills. Bottom end and rod bearings. Couple more bills (parts only). Seals. Haven't priced a set but you now have to piece a set together I believe. Just depends how how much your love your bike and can afford to spend.

If it's been running good with no oil consumption and you're really concerned I'd at least check the compression, clean it up and reinstall. You can easily spend $2000 on a simple rebuild and as much as $5000+ on a performance rebuild.

swan · « **Reply #6 on:** January 25, 2009, 07:17:13 PM »

Twice as much and three times longer than you think.

Bill Vaughan · « **Reply #7 on:** January 25, 2009, 08:35:47 PM »

I agree with the others who weighed-in already - it impossible to tell until you open it up. That said, if you're looking for a point of reference, I just went through my 550 from top to bottom for under $1,000. No major problems, however. Replaced rings, seals, gaskets, tensioner, guide, a few shaft bearings, rebuilt the carbs., and did some cosmetic work (cases painted/covers polished).

Geeto67 · « **Reply #8 on:** January 25, 2009, 10:01:12 PM »

does it smoke or burn oil?

if the motor doesn't need a rebuild then don't fcuk with it at all. These engines are good for 50K+ if maintained. If your curiosity can't be helped then at the very least do a valve guide job on the head as the 77/78 heads have a problem with wearing through the valve guides. You will still get 30-40K out of one if you are not beating on it so if you have a bike with under 10K plus miles then put the motor back in the frame and put it out of your head, chances are you will have gotten sick of the bike and sold it long before it will give you problems.

from a cost standpoint a stock motor rebuild will cost you more than the bike is worth, and a performance rebuild will cost you $500-1000 more. Honestly if your motor does begin to develop problems it is usually cheaper to buy another engine and swing it in than rebuild, It is what I do and I have actually rebuilt a cb750 engine before (only once it is so time consuming and I don't have the patience to do another). a used cb750 engine will cost you between $100-$500, a rebuild in parts alone if you go the cheapest route and do all the work yourself usually ends up being about $300 (this is with new rings, a cylinder hone, laping the valves, and a new timing chain and adjuster.

cafe2be · « **Reply #9 on:** January 26, 2009, 05:56:18 AM »

These are the answers I am looking for. The motor runs fine for now. Just thinking of having someone replace all the gaskets and check to see if anything is wrong internally. Oil pump inspection etc.. I hear you on replacing the motor with another. Well you guys answered my questions. I will just clean her up, paint and slap her ass back into the frame.

Gordon · « **Reply #10 on:** January 26, 2009, 07:04:49 AM »

Quote from: swan on January 25, 2009, 07:17:13 PM

Twice as much and three times longer than you think.

The best answer yet!!

paulages · « **Reply #11 on:** January 26, 2009, 07:33:09 AM »

cb750 rebuild with gaskets, o-rings and seals, head cleaning and seats reground, cylinder bore and hone, primary and cam chains with associated parts costs my under $500 in parts and machining.

OakBehringer · « **Reply #12 on:** January 26, 2009, 08:16:03 AM »

Dude, if you have even and good compression and you're not burning oil, do NOT open up your engine. You're wasting your money. Buy a non-running project bike for $200 and tear that apart.

pablo78cb550 · « **Reply #13 on:** January 26, 2009, 08:43:53 AM »

i had honda do my engine. $1200.00

Duke McDukiedook · « **Reply #14 on:** January 26, 2009, 09:25:01 AM »

Quote from: pablo78cb550 on January 26, 2009, 08:43:53 AM

i had honda do my engine. $1200.00

What all did that include for $1200 Ameros, Pablo?

pablo78cb550 · « **Reply #15 on:** January 26, 2009, 09:34:09 AM »

rings pins gaskets valves guides honing pretty much everything from the base gasket up. excluding the pistons. they where fine.

checkflag · « **Reply #16 on:** July 03, 2009, 10:06:05 PM »

Sorry to bring this one back to life, but it seemed like my question would be fitting.

I don't know a whole lot about rebuilding these motors, but what is a "valve guide" job,
and how much would this cost? would this involve a complete engine rebuild, or just in the
top end.

B.O.X.N.I.F.E. · « **Reply #17 on:** July 03, 2009, 10:13:35 PM »

Quote from: swan on January 25, 2009, 07:17:13 PM

Twice as much and three times longer than you think.

This has been absoultely true of my bike. Same with my 49 Chevy, which I started in 06 and thought I'd be driving sometime at the end of 07 (cab is still off the frame).

MJL · « **Reply #18 on:** July 04, 2009, 12:27:30 AM »

Quote from: checkflag on July 03, 2009, 10:06:05 PM

Sorry to bring this one back to life, but it seemed like my question would be fitting.

I don't know a whole lot about rebuilding these motors, but what is a "valve guide" job,
and how much would this cost? would this involve a complete engine rebuild, or just in the
top end.

Valve guides are the holes the valve stems ride in. It does not involve the entire motor, just the head.

To the OP, I spent $100 on a good stock motor. If I was to rebuild my current motor, i"d spring for a 836 kit and a cam, but that's just me.

checkflag · « **Reply #19 on:** July 04, 2009, 12:35:13 AM »

Quote from: MJL on July 04, 2009, 12:27:30 AM

Quote from: checkflag on July 03, 2009, 10:06:05 PM

Valve guides are the holes the valve stems ride in. It does not involve the entire motor, just the head.

thanks. Any idea what that would cost? Here's the thing, I have my eye on a 78 cb750f ss.
it has 47k on it.. I'm told it runs great, no blue smoke or nothing, but i also hear to watch out
for this kinda issue on these bikes. Ill probably get the bike, but I would like to know what I
would pay for this job if it came up.

MJL · « **Reply #20 on:** July 04, 2009, 12:38:42 AM »

MReick is the guy to talk to about that. He is the resident head expert.

crazypj · « **Reply #21 on:** July 04, 2009, 10:27:59 AM »

Depending on where you get guides and what material they are, you have to strip head, heat to 325~350 degrees, knock out old guides, cool it down and check head holes are not already oversize, ream head for next size if it is, re-heat head, fit new guides, ream to size and re-cut valve seats.
Bronze guides are about $18.00~30.00 each, depending on supplier and availability, seat cutting, about $25.00~40.00 per seat, 3~7 angle, porting extra but its usually done as price per head, anything from $700.00 to $1400 for inline four complete re-build.
If your doing it as a hobby, the time taken is longer but the costs are reduced.
As a full time job, time is money so its done as soon as possible but costs more because you probably like to eat at least once a day
I've done both, its probably why I have so many unfinished projects now and don't do any work for other people (got some of a CB350 racer that was started 5~6 yrs ago, cant even find the guy who owns it)

PJ

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Author Topic: general cost to rebuild a motor. (Read 15971 times)