Topic: new bought, old engine rebuild

[pjlogue]

I purchased an old 750 engine to use as a rebuild for my 750.  Engine was listed as 16,000 mi and exterior looks good.  upon pulling the head and jugs I found the cam and cam carrier to be almost pristine condition.  same with the rockers and cam chain roller. 

My engine that is in my bike sounds like an old washing machine because the tensioners are warn.  My thought is to rebuild the motor I bought and swap it for the one on the bike. 

Has anyone had experience with Cycle-x products and their work?  The cam and primary drive tensioners have a real hefty price and I wonder if the price is worth it.  I am pushing 70 years old and do not beat on my bikes.  Strictly enjoyment riding. 

My thought is to have Cycle-x replace the valve guides and re-cut the valve seats.  I will then lap the new valves and polish the cylinder heads/exhaust paths.  Polishing the inside of the heads and exhaust tracts keeps the exhaust gas temps high and reduces heat transfer to the engine. I have done this with several engines on my cars and the result is very noticable with fuel economy. 

Has anybody used Cycle-x tensioners?  Specifically their runners, not the roller tensioners. I'm willing to put the $ into this engine if the cost warrants it.  Granted, the engine I'm building will outlast me but it's not about my lifespan.  What I build is about longevity of the project.  Hopefully, in 50 years and I'm long gone this bike will still be running.

-P.

[Pbeattie89]

I have bought from Ken at cyclex before, and he is a really nice guy. He is very passionate about the old cb750s. His slider tentioners are likely overkill for a stock engine, but my thought are that they will likely outlast the oem conventional roller style. My other concern with NOS honda parts is that the plastic/rubber parts are likely quite old and deteriorated, so their longevity is questionable. Give Ken a call, and he will steer you right for your goals.


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[Don R]

 I'm aware of other people's attempts at improving the tensioners that didn't work out. I'm sure Ken has done his homework and am considering the same upgrades. Hopefully someone can verify the value of the improvements.
 

[69cb750]

I have bought from Ken at cyclex before, and he is a really nice guy. He is very passionate about the old cb750s. His slider tensioners are likely overkill for a stock engine, but my thought are that they will likely outlast the oem conventional roller style. My other concern with NOS honda parts is that the plastic/rubber parts are likely quite old and deteriorated, so their longevity is questionable. Give Ken a call, and he will steer you right for your goals.

Have replaced several primary tensioner and cam chain tensioners.
Parts are new (not ancient) rubber is nice.
13620-300-010 - https://www.ebay.com/itm/326196859595
14500-300-000 - https://www.ebay.com/sch/i.html?_from=R40&_nkw=14500-300-000&_sacat=0&_sop=15&rt=nc&LH_ItemCondition=3

[pjlogue]

I appreciate the input.   My aim is a very smooth running engine.  I will reach out to Ken at Cycle-x.  I want to build an engine that has the cylinder bores straight, crank shaft straight as well as cam shaft.  The cam shaft I have is within 0.003 " I can tweak it to within 0.001.  I have to see what the run out is on the crank shaft.  I am not sure what value it would be to have the crank shaft balanced with Cycle-X  I want to replace the cush bushings in the motor while I'm in there. I'm pushing 70 years old.  I  have had this 750  since I was 20.  The best thing I can do is to keep the bike like/better than new condition.  Some day, some kid will have this bike and say "holly #$%*" look what I bought from an old geezer.

-P.

[bryanj]

Send the head to M Reick on here for guides,seats and porting. His work is absolutely the dogs. Not sure if he does the cranks as well

[Pbeattie89]

I have bought from Ken at cyclex before, and he is a really nice guy. He is very passionate about the old cb750s. His slider tensioners are likely overkill for a stock engine, but my thought are that they will likely outlast the oem conventional roller style. My other concern with NOS honda parts is that the plastic/rubber parts are likely quite old and deteriorated, so their longevity is questionable. Give Ken a call, and he will steer you right for your goals.

Have replaced several primary tensioner and cam chain tensioners.
Parts are new (not ancient) rubber is nice.
13620-300-010 - https://www.ebay.com/itm/326196859595
14500-300-000 - https://www.ebay.com/sch/i.html?_from=R40&_nkw=14500-300-000&_sacat=0&_sop=15&rt=nc&LH_ItemCondition=3

I didn't realize that they were still manufacturing these components.

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[PeWe]

Really replace valve guides after only 16,000 mi? 
If they are in need of replacement, cam and rockers should show wear due to wrong/no oil or similar.

Too low viscosity oil by purchase or wear due to hot weather/not changing oil. Maybe lean jetted carbs on top of that.

When head is out, remove springs and check each valve when its lift is ca 10mm, wiggle it sideways. You should not get any clunky feel and see the valve move sideways.
You do not need to be an expert to verify that.

Bores, pistons and rings should be ok too after that low milage.

I guess the chains are ok too, tensioners might be hard.
Small black rubber pieces can show up in oil from the old tensioners.

Clutch fiber plates can be too old.
I have used Cruzin Image cheap clutch with 836, ca 80 whp without slip.
My almost stock K2 use them.

My +100whp K6 970cc runs fine with stock chain tensioners. But use heavy duty chains. Street bike, not racing but some occasional heavy acceleration beyond rhe road signs recommendations happens

[pjlogue]

Send the head to M Reick on here for guides,seats and porting. His work is absolutely the dogs. Not sure if he does the cranks as well

Who is M Reick?  Do  you have a contact for him?

I have done porting/polishing of cylinder heads but do not have experience with replacing valve guides or cutting valve seats.  It is a job I would rather have someone with experience do rather than do the learning cuve on a part that is hard to replace if I muck it up. 

-P.

[bryanj]

Member on here MRieck , look up the members and send him a pm

[pjlogue]

Really replace valve guides after only 16,000 mi? 
If they are in need of replacement, cam and rockers should show wear due to wrong/no oil or similar.

Too low viscosity oil by purchase or wear due to hot weather/not changing oil. Maybe lean jetted carbs on top of that.

When head is out, remove springs and check each valve when its lift is ca 10mm, wiggle it sideways. You should not get any clunky feel and see the valve move sideways.
You do not need to be an expert to verify that.

Bores, pistons and rings should be ok too after that low milage.

I guess the chains are ok too, tensioners might be hard.
Small black rubber pieces can show up in oil from the old tensioners.

Clutch fiber plates can be too old.
I have used Cruzin Image cheap clutch with 836, ca 80 whp without slip.
My almost stock K2 use them.

My +100whp K6 970cc runs fine with stock chain tensioners. But use heavy duty chains. Street bike, not racing but some occasional heavy acceleration beyond rhe road signs recommendations happens

I appreciate the input.  16K  mileage on a ebay purchase does not mean much.  it depends on the care  an engine had.   My ex brother-in-law was absolutely brutal with mechanics.  He could destroy a car engine in less than 6 months!  I cringe when I think of this.  Ideally, this rebuild will be a smothe  running engine.  I'm pushing 70 now and building an engine that lasts for another 48 years would be nice but reality is I'll be taking a permanent dirt nap by the time this engine gets in rough shape. 

-P.