Topic: CB750: Aware of cheap parts -tensioner rubber cracked in 2- Carb boots cracking

[sbeckman7]

Yikes.. after reading this I am hoping I didn't just do the same thing by purchasing these carb boots 

http://www.ebay.com/itm/141877529667?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[grcamna2]

Just ordered their engine seal kit today. Will stay away from their other parts.
Thinking about making a primary tensioner roller from Delrin, how would you think it would hold up?

I have one on a CB350 twin and it's holding up well.

First off I'm not at all questioning your abilities, but herein lies the problem. How do you know it's holding up well? Maybe you had it apart to check, don't know. On my racebike I had to make a drive chain guide because of the swingarm angle and tried different materials. Delrin lasts one season. Maybe an internal roller with lots of lubrication will survive better, but it's just not easy to check.

I bought a pr. of them from a man who machined them from 'PA6' (isn't that the same thing as Delrin?)and they are white.I've had the engine apart after 5000 miles w/ no appreciable wear.

Well now we're comparing apples to oranges. The original post in this thread addresses specifically those cam chain tensioners distributed by Vintage CB750. Your custom machined rollers from an as yet undetermined material doesn't really shed any light on the durability of the tensioners sold by Vintage CB750. Those of us that may have fallen victim to substandard materials from Vintage CB750 are facing engine disassembly (or engine failure) just to find out.

I think the 'PA6' material holds up well and the rollers are interchangeable from that bike to the CB750.The same man in Poland is starting to make them out of steel similar to the Cappelini(spelling might be off)design which is used in CB350 twin race bikes.

[Wingnut74]

So I decided to unbutton the head I just tightened up to fish out the Vintagecb750 cam chain tensioner I just put i last week. OEM parts on the way. I used a NOS Honda head gasket and had tightened it up to 15 lbs. When I took the head off I carefully tried to separate the head gasket but a few small spots of the thin paper layer on the bottom of the gasket stuck to cylinder and separated from gasket. the gasket is now shiny and not tacky. Can I reuse it and maybe touch up the few little spots - 5 spots about the area of the O on your keyboard. If so maybe Permatex 1 skimmed over the little thin depressions in the gasket? or suck it up and new gasket? thanks

[hotdog]

So I decided to unbutton the head I just tightened up to fish out the Vintagecb750 cam chain tensioner I just put i last week. OEM parts on the way. I used a NOS Honda head gasket and had tightened it up to 15 lbs. When I took the head off I carefully tried to separate the head gasket but a few small spots of the thin paper layer on the bottom of the gasket stuck to cylinder and separated from gasket. the gasket is now shiny and not tacky. Can I reuse it and maybe touch up the few little spots - 5 spots about the area of the O on your keyboard. If so maybe Permatex 1 skimmed over the little thin depressions in the gasket? or suck it up and new gasket? thanks

Good move by the looks of it, suck it up and install a new gasket and have peace of mind.

Sent from my HTC_M9u using Tapatalk

[madmtnmotors]

PeWe, I would at least like to by you a beer! 

    Upon disassembly of my recently assembled motor I have to concur with PeWe's evaluation of the substandard components being distributed by the aforementioned e-tailer. The tensioner that I just extracted from my own engine, with less than 2000 miles, is already showing signs of immanent failure. The failure is difficult to capture in pictures, and the tensioner wheel had not started to break apart yet, but there are cracks and splits both radially (around) and axially (across) the wheel. On top of that, these wheels are incredibly soft as demonstrated by the amount of deflection I am able to achieve with just my thumb and forefinger of one hand (I had to hold the camera with my other hand).


At rest there is just a hint of what lurks underneath:




Add a little (a lot?) of deflection and a freaking gap opens up:




Another section of the wheel at rest:




Get a load of the amount of deflection I can impart with just two fingers, as well as the amount of separation already underway:




That was quite a bitter pill you served up there PeWe,  but I'm glad you did  . I was actually trying to sell this bike, and this could have ended badly for the new owner. This extra effort was well worth it as far as I am concerned and has proven to be a valuable lesson learned.

The extra labor involved has also motivated me to keep this bike. Looks like the new 4th over pistons and fresh cylinders will go on my "old reliable" ride and this one will get the CI 836cc treatment along with a Webcam 41 to help it breathe. Some APE HD cyl studs to round it out and I should be able to shave two seconds from my 1/4 mile E.T. ...

Now look what you started! 

[grcamna2]

That rubber cam chain roller you just posted pics of is Way too flexible to truly support that cam chain under load.. I hope you members will install solid rollers.

[kmb69]

.....
The extra labor involved has also motivated me to keep this bike. Looks like the new 4th over pistons and fresh cylinders will go on my "old reliable" ride and this one will get the CI 836cc treatment along with a Webcam 41 to help it breathe. Some APE HD cyl studs to round it out and I should be able to shave two seconds from my 1/4 mile E.T. ...

Now look what you started! 

Sorry to hear about the problems    but happy to hear about the motivated re-direction  .

Let me suggest you consider the Kibblewhite HD studs from Cycle-X instead of the APE product. The Kibblewhite product is superior in my opinion and none have been reported broken. Cannot say the same for APE. I know Jay stands behind them and will replace a broken stud but why risk the potential hassle when a better product is available. 

[madmtnmotors]

Sorry to hear about the problems    but happy to hear about the motivated re-direction  .

Let me suggest you consider the Kibblewhite HD studs from Cycle-X instead of the APE product. The Kibblewhite product is superior in my opinion and none have been reported broken. Cannot say the same for APE. I know Jay stands behind them and will replace a broken stud but why risk the potential hassle when a better product is available. 

Well, I was going to race something one way or another! This one has run so well and shifts so smoothly since putting in the 4th over pistons just 1700 miles ago, and my regular ride is pretty tired, so looks like both of them are getting a facelift!

I'll definitely consider the Kibblewhite studs. I've had enough practice putting this together and taking it back apart!

[PeWe]

Sorry to hear about the problems    but happy to hear about the motivated re-direction  .

Let me suggest you consider the Kibblewhite HD studs from Cycle-X instead of the APE product. The Kibblewhite product is superior in my opinion and none have been reported broken. Cannot say the same for APE. I know Jay stands behind them and will replace a broken stud but why risk the potential hassle when a better product is available. 

Well, I was going to race something one way or another! This one has run so well and shifts so smoothly since putting in the 4th over pistons just 1700 miles ago, and my regular ride is pretty tired, so looks like both of them are getting a facelift!

I'll definitely consider the Kibblewhite studs. I've had enough practice putting this together and taking it back apart!

GOOD news for me! It is not a single case of bad quality. I had thoughts from the beginning about the soft rubber. But I was sure that tests have been done to verify the product.
Rubber must cope with the temperature, oil and the forces pressing agans chain and forces from chain when accelerate/decelerate.

About cylinder studs. I have also broken one APE stud. This ended up in purchase of torque wrenches so I have own.
I could verify over torqued nuts. My new wrench indicated 36Nm to make it to move further. 30,5Nm is 22.5 ft lbs which is max.  The wrench I had used was borrowed from the lab at my job. Bad wrench is not cheap.

I replaced all when I could not trust the over torqued studs. I bought new Kibblewhite studs that has same max torque as APE.
22.5 ft lbs

My conclusion:
HD studs are hard and stiff with min flex that will keep things together. Important to not torque too much!
I torqued with max 28Nm (20.65 ft lbs). Retorqued after 24 hours and after some driving when I changed cam and did some thread work. (I can do that without pulling engine)

Edit: The beer will taste good! It would be fine to have a long trip around on my bike and meet guys on this forum. The distance is an issue though...plus all water between Europe and USA

[madmtnmotors]

GOOD news for me! It is not a single case of bad quality. I had thoughts from the beginning about the soft rubber. But I was sure that tests have been done to verify the product.
Rubber must cope with the temperature, oil and the forces pressing agans chain and forces from chain when accelerate/decelerate.

It never occurred to me to do a "pinch test" on freaking tensioner wheels. I agree, anybody selling these types of components should at least test ONE of them for suitability for their intended purpose. As far as I'm concerned the conduct by the manufacturer of these is borderline criminal. 

The beer will taste good! It would be fine to have a long trip around on my bike and meet guys on this forum. The distance is an issue though...plus all water between Europe and USA

Yeah, water and bikes don't mix! 

[mystic_1]

The beer will taste good! It would be fine to have a long trip around on my bike and meet guys on this forum. The distance is an issue though...plus all water between Europe and USA

Yeah, water and bikes don't mix! 

Mythbusters proved it could be done, if you go fast enough

[PeWe]

Not even Queen Mary 2 take bikes....

[grcamna2]

LOL 

[Wingnut74]

Holy Crap do I feel lucky that PeWe and Madmtnmotors posted this when they did! I feel like I owe you guys more than a beer - more like a keg. Had just sealed this part in on the bench a week ago.  NOS OEM stuff arrives Saturday - doing the slipper/guide too.  BTW for anyone else that is doing this MRieck, who knows a lot, said that you can lift the cylinders up just enough to replace the tensioner without having to redo the whole compress the rings into the cylinder thing. Probably no biggie to the pros around here, but for hacks like me who are paranoid of damage - that took forever to get rings in. When I was doing the rings I used hose clamps and ended up spinning them around a bit to get the rings in. At the end I realized I had no idea where the ring gap alignment landed. Should I sweat this and redo? and if I have brand new NOS +1mm pistons and rings, is it pretty hard to bust a ring / score the cylinder? thanks

[grcamna2]

Holy Crap do I feel lucky that PeWe and Madmtnmotors posted this when they did! I feel like I owe you guys more than a beer - more like a keg. Had just sealed this part in on the bench a week ago.  NOS OEM stuff arrives Saturday - doing the slipper/guide too.  BTW for anyone else that is doing this MRieck, who knows a lot, said that you can lift the cylinders up just enough to replace the tensioner without having to redo the whole compress the rings into the cylinder thing. Probably no biggie to the pros around here, but for hacks like me who are paranoid of damage - that took forever to get rings in. When I was doing the rings I used hose clamps and ended up spinning them around a bit to get the rings in. At the end I realized I had no idea where the ring gap alignment landed. Should I sweat this and redo? and if I have brand new NOS +1mm pistons and rings, is it pretty hard to bust a ring / score the cylinder? thanks

You need a helper..,me too

[Wingnut74]

Two helpers - step blocks A & B, One step at a time. Also here is my pre-surgery prep for a Tensioner-ectomy. Wire to hold the gasket up and out of the way and preventing crank case disaster on roller disassembly.

[754]

Pewe how many times have you pulled the frame section out ?

[Davidov]

Was the engine making a ton of noise? Clattering?

I also have this tensioner in place.

[grcamna2]

Boots are easier to see when cracking and replaced within an hour or 2. Worse with the cam chain tensioner that need an open chain. I will not open cam chain, cases to be apart.
I was lucky when I cannot see any damage and cases to be apart anyway. I had to warn others.

The metal cam chain tensioner might be a better choice, no rubbers that can crack or be found as small parts in the oil pump mesh.
http://www.ebay.com/itm/Honda-CB250-CB350-CL350-SL350-CB750-Cam-Chain-Tensioner-Roller-Wheel-Set-/231576401099

I've gotten in touch w/ this seller and he manufactures them right here in SW PA. near Pittsburgh in this area,he sent me some installation info on this set.

[Davidov]

We need to make a list of anyone who has bought this kit and demand total refunds.

Would I be able to reuse any of the gaskets? Base, head, valve cover?

[madmtnmotors]

We need to make a list of anyone who has bought this kit and demand total refunds.

Would I be able to reuse any of the gaskets? Base, head, valve cover?

Well, according to Wingnut's communication with them they have "sold over 500 with only one complaint". PeWe stumbled on this problem based on a "gut feeling" more than anything. That means there could be 500 people out there that are in one of several potential positions:

>They sold the bike and the new owner has no clue
>They have not put enough miles on it to notice
>They suffered a broken cam chain and blamed the chain

or, least likely:

>PeWe and I happen to be the only two that received parts from a "bad batch"

I personally am just chalking this up to lesson learned and can only encourage others to use genuine Honda parts at the cam tensioner location, or a tried and true aftermarket source of heavier duty components. I know my days of "crash test dummy" beta tester are over. I'm just glad I caught it before the rollers self destructed and fouled the engine with little bits of rubber like what happened to PeWe.

[PeWe]

We need to make a list of anyone who has bought this kit and demand total refunds.

Would I be able to reuse any of the gaskets? Base, head, valve cover?

Well, according to PeWe's communication with them they have "sold over 500 without any complaints". PeWe stumbled on this based on a "gut feeling" more than anything. That means there could be 500 people out there that are in one of several potential positions:

>They sold the bike and the new owner has no clue
>They have not put enough miles on it to notice
>They suffered a broken cam chain and blamed the chain

or, least likely:

>PeWe and I happen to be the only two that received parts from a "bad batch"

I personally am just chalking this up to lesson learned and can only encourage others to use genuine Honda parts at the cam tensioner location, or a tried and true aftermarket source of heavier duty components. I know my days of "crash test dummy" beta tester are over. I'm just glad I caught it before the rollers self destructed and fouled the engine with little bits of rubber like what happened to PeWe.

Hi guys,
I have not communicated anything with the seller about these parts.

No idea since I bought them summer 2012. I complained about weak Ultimate coils with almost no responce, except no warranty since I bought them 1,5 years ago, but used them a few months when failure finally was detected.

Only thing I can do is to warn people here about not acceptable quality.
I had planned to replace the cam chain tensioner anyway when I tear the the engine down for crank and trans replacement. I understood that I should at least use Honda parts. I regret the cheap Taiwan made tensioner rather soon after install 2013 when I remembered the soft rubber. I did not realize it should crack this quick after max 3000 miles, probably less.

Warranty is max 1 year.
Engine parts I do not know when they can claim wrong use. Better to buy important parts of good quality. Remove cylinder again for tensioner replacement is not nice.
This opens up for frame mod that Frank sell (754). Cut frame and be able to remove head and cylinder without pulling the engine. No need of drain oil and disconnect cables hoses and........ This makes the job much easier. One of the best mod I have done.

[PeWe]

Was the engine making a ton of noise? Clattering?

I also have this tensioner in place.

NO, I did not hear any extra noice. The cracked rubber was a surprise when I lifted the head and prepared cyl lifting. My engine has less chain rattle since I installed CCC HD prim chains which are tighter than OEM.

[PeWe]

Pewe how many times have you pulled the frame section out ?

I have lost the count... :-) This mod should be mandatory. The trigger for me was a broken HD cyl stud that I read about on this forum. A guy broke a stud a few years ago when tighten head, replaced that stud only and got another failure a few years after when driving with a really bad result with broken cam, chains etc. etc.

I had broken one stud and replaced that one only. So I had to fix it. I found that I had overtightened all of them and I replaced all after the head was off. Head sent to shop for refurbish too.

After that cam change 4 times, and fix cam holder threads. Total 5-6 times plus this engine tear down I do now.  About 7 times during 2 years.
Easier to pull engine with head, cylinder, pistons (and cyl studs) off.
I change cam with coils still mounted.

The thread were some guys did the frame mod. I recommend how I cut my frame. Max opening that fit Mikuni smoothbore VM29 and TMR 32. Should not be any problem with OEM either.
http://forums.sohc4.net/index.php/topic,62832.msg1505097.html#msg1505097
http://forums.sohc4.net/index.php/topic,62832.250.html

Pulled engine yesterday. Lifted it out alone with a sling strap around cases that made it much easier. NO finger problems and other collateral damage. A friend will help me to lift up on the bench. I do not need damaged myself like the spine.
http://forums.sohc4.net/index.php/topic,61168.msg1777045.html#msg1777045

[madmtnmotors]

Hi guys,
I have not communicated anything with the seller about these parts.

My bad. I was going by what I thought I remembered (memory is shot) instead of rereading back through the thread.    Previous post corrected.



Found it! It was Wingnut that had reached out to Vintage CB750, not PeWe:

For what its worth, I followed up to ask VintageCB750.com about whether they had seen reports of this before - trying to figure if I am going back in my newly buttoned up head and cylinders to get it out. They said they have sold around 500 of these cam tensioners over 6 years with only 1 report of this issue.