79cc HF Death Rattle....

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PoorBoy

New Member
May 31, 2014
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CA
Finally got my 79HF/Dyno on the road for a maiden run this morning. Sorted out several challanges that are all overcome except for one. The engine had a "rattle" like real loose lifter adjustment. Checked them and were at .005. Seems ok to me at this time. Started pulling the engine apart until I found the noise to be the back side of the cam gear. Hoping someone can tell me what the function is of the spring loaded weight on the back side of the gear. Compression release? And can it be disabled with the engine used on a bike. It just sounds like loose marbles when the engine is running. Hard to believe it should sound like it does.

I appreciate your help and knowledge with this. I tried to search using terms I thought were right but I guess not.

Once I get this dealt with, the bike comes apart and off to the powder coat shop to finalize the build. Certainly learned a lot on this build with all the shared knowledge here.

Thanks, Tom
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
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38
Ridin' inSane Diego, CA.
Hey Tom, are you sure the rattle is coming from the engine? I don't think the compression release is the culprit here so I'd leave it alone for now and keep trouble shooting. It can be made inoperable if you know what you're doing, but I wouldn't suggest that. Did you take the cap off the piston rod at anytime or disconnect the governor completely?

Keep feeding information but don't run the engine for any longer than you have to to figure this out....
 
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PoorBoy

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May 31, 2014
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Scotto,

I did remove the governor completely. Adding the bolts to block off the open holes. The bolts are short enough that they do not interfere. I have not removed the rod cap at all as I felt there has been no reason to do that. There appears to be no evidence of any interference inside the crankcase and the oil drained out had what I would expect to see from a new motor. Very very small metal bits from the break in operation. I owned and operated a VW engine and transmission rebuilding shop for 34 years so I have a feel for unusual engine and trans sounds. But maybe this is just the sound from this beast. Everything looks tight inside.

I hear the clutch bell from the "quality" high torque clutch I am using at this time. It isn't chain noise as the sound occurs just applying throttle at idle. I added 8oz of oil to the engine. Perhaps after some reading last night in the archives, 11oz would be better? What say you guys?

Back together it goes this morning if time permits and I will trouble shoot more or just run it.
 
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FFV8

New Member
Oct 29, 2013
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Spring Valley NV
You will want to keep the compression release. It will make the pull start components last a lot longer.

The compression release should be against it's stop & pretty quiet at idle speed. It will make noise during cranking for sure.

Splash oiled plain bearing engines are a different animal than a VW.
The dipper must get a good swipe through the oil, at all speeds. sometimes a little higher oil level helps. Idle speeds should be high enough to get good oiling, 1400 to 1550 RPM is good. Idling a splash engine too low can be hard on it.

Is your engine mounted flat, or have you tipped the mounting base from the original design? I have a GX120 mounted at an odd angle, and it takes a bit more oil to maintain good dipper contact.

We run Rotella 15W40 in the splash engines here in the desert. A little Lucas additive can help with the noise too. I try to make sure any oil / additive mix I use has at least 1000 ppm of Zinc. The newer cars do ok with the zinc removed, but flat tappets & splash oiling were designed when zinc was in every motor oil.

.
 
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PoorBoy

New Member
May 31, 2014
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FFv8,

I appreciate your response. Yes the engine is mounted where the cylinder is almost vertical in the frame. I will put it back together and add additional oil for assured splash. 11 ozs hopefully may help. And I will look into oil additives that will benefit the engine also. I am sure the Lucas products are local to me, being in Orange County.

Looking forward to getting a better clutch in the near future and layback seat post too.

Thanks for your time and great suggestions!

Tom
 
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FFV8

New Member
Oct 29, 2013
551
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Spring Valley NV
Lucas oil stabilizer in on the shelf in every chain auto parts store in north america. An ounce per quart is recommended - I mix it in to a fresh quart of oil.

For oil level, look at where it would be with the engine mounted as intended. Draw an imaginary line across the top of the filler parallel to the mounting base. We usually run the oil all the way up to the top of the threads to make up for leaning / stopping / starting.

Once you have that line, look at how far it is from the crankshaft centerline. My GX120 is mounted straight up. i made a dipstick to measure the same height from the crank centerline & fill the engine accordingly.

Clutches make a little noise as the shoes hit the bell. I prefer the Hilliard Extreme duty units, because they are easy to tune & all of the wear parts are available.
I just saw a maxtorq die in 3 months on the street on a friend's bike with a 79. The bushing was gone, & the spring was shot. Not a thing worth fixing.

.
 
runnermike

runnermike

Member
Nov 18, 2012
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Sanford, FL
Is there a way you can take a video and post it to youtube with a link for us. I have a HF 79cc and havent heard any unusual noises, but then again, my exhaust is a tad on the louder side. Let us know what you find out.
 
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PoorBoy

New Member
May 31, 2014
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CA
Actually, Runnermike, that is a very good idea. I will tray and upload a video tomorrow. But I am not finished with the bike so it looks a bit shabby at this time.
 
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PoorBoy

New Member
May 31, 2014
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CA
Ok, so I uploaded a video of my concern to YouTube at:

http://youtu.be/1bbu4Yw0Mq8.

I am not concerned with the clutch bell ringing which may be present. Removing the clutch, JS chain and running the engine, the sound remains. Like I mentioned, when I opened up the crankcase, no real metal indicating something drastic. Perhaps I need to just turn up the radio like some of my client did when they heard a noise while driving. LOL

Anyway, thanks for any and all input. Need to get a real clutch and clutch/chain guard, try tuning the carb and then get the frame powder coated (white with some black fine pin striping).
 
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PoorBoy

New Member
May 31, 2014
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CA
Thanks for your time spent with this, Runnermike. I will run it as is. At last the cost of the motors is cheap compared to most of the other stuff on this bike. Should it need replacement.
 
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