6.5hp clone engine vibration at certain RPM? Help!!!

philbo

philbo

New Member
#1
#1
Hi guys! Thanks in advance for any helpful ideas!

When I rode the Baja around I noticed a really bad vibration at a certain rpm. I'm guessing I'm doing about 15-20mph? That's a guesstimate.

I took off the jack shaft chain to isolate the problem from the suspension And chains (in case they were loose I I don't have a chain tensioner on the jacks haft chain-gone when I got the Baja) and the vibration appears to be from the engine.

To make sure it isn't a loose engine plate like the welds broke I pressed down on the engine with my foot and the vibration didnt change.

Below is a video. I start the engine at idle then gradually increase the revs.

6.5 hp clone engine, vibration at certain RPM. - YouTube

At 5 seconds revving up then 25 seconds coming down off the revs one can notice the gas tank shaking( I need to fix the rear mount!) and can hear the engine rattling. Once at that RPM where it vibrates if I rev more the engine smooths out.

Is this a normal vibration at this RPM? Just ignore it?

The governor linkage was removed by the previous owner. You think the internal governor gear and weights are doing this?

I figure if it was a crank or cam bearing it would continuously vibrate and get worse as the RPMs increased, yes?

The previous guy replaced an intake valve that snapped. Just extra info.

Thanks!!!!
 
philbo

philbo

New Member
#3
#3
Hi gumpit! Thanks for the reply. The clutch is on. That is a great idea though. Ill take that off to further isolate the problem.

After taking off the clutch if the vibration is still there I might crack open the crankcase to further isolate the issue by removing the guts of the governor since the linkage is missing. Ill look at the crank and cam and the bearing journals to see what condition they are in as well. See when I get a chance to do that. Thanks!
 
philbo

philbo

New Member
#5
#5
Thanks for the reply, newoldstock.

It vibrates pretty good. Like teeth chattering vibrate. Just weird it's at a certain rpm revvin up them comin down in the same spot.

It does smooth out when I rev it more, at least with no chain hooked to it. Maybe once I button it up and go for a drive ill give it more gas and see if it smooths out. I might just avoid that rpm range. When I was driving it last and it vibrated I didn't give it more gas. Ill try it to see if it smooths out at a higher rpm.

I sometimes wonder if it vibrates at the speed when the governor supposed to kick in? Again, the previous guy took off the linkage.

Thanks for the input guys.
 
philbo

philbo

New Member
#8
#8
HI Dan, how are you? :smile:

Yes, the rear mount of the gas tank is shot and will be on the "to do" list :rolleyes: .

I did point out in the video to look at the gas tank vibrating just so people could get a sense of when the vibration was happening as the sound was not really indicative of when the vibration occurred. Call it a visual cue since one couldn't feel the vibration in the video. :thumbsup:

The source of the vibration isn't the loose gas tank. I think it's internal to the engine. I had my foot pressing down on the tank when there was the vibration and it still vibrated like crazy at certain RPMs.

I took off the clutch as gumpit mentioned. Still vibrating.

The shaft of the crankshaft where the clutch is mounted does not appear to be vibrating, at least on a quick visual.

Weird though. The lever for the governor is attached to the casing and I have actually no idea if only the linkage for the governor was taken off or if the previous owner actually went in to take the governor parts out as well.

I mention this because when I rev the engine, I don't feel anything/resistance against the arm, even at different RPMs, assuming that I'm revving the engine enough to get the governor to kick in. :shrug:

I think I really want to take the side cover off to see what's cooking inside while I have the other stuff off.

The vibration saga continues... :confused: :hammer: :blink:
 
philbo

philbo

New Member
#11
#11
Thanks for the suggestions guys. :thumbsup:

Hope it's not a rod bearing. Flywheel. Hmmmm...I 'll have to check into that. Thanks!

I'll see when I get a chance to play with the engine...
 
philbo

philbo

New Member
#12
#12
Newoldstock said:
My wife really like a 160 I had.
Click to expand...
Are you talking a Honda 160? If that's like a 5hp engine, yes?

I saw a couple of those and I was thinking a Honda engine would be cool but didnt want to go down on the power. If anything I want to go up.

Looking into what engines came with a 3/4" crank. Some 8 hp Briggs and strattons did I think.

If I'm patient come spring I may even see some snowblowersa on the free section of Craigslist if I keep my eyes open.

Thanks!
 
philbo

philbo

New Member
#14
#14
Aha. Gotcha. 160 clone. I see some Honda 160,196,200 engines going for like $100-$150. They look pricey figuring a new predator 212 goes for like $99 on sale at harbor freight. Just wondering if he Honda quality is worth the extrat price.

Figure 6.5hp is the same regardless if the engine make. Figure if hey advertise 6.5hp that it makes 6.5hp regardless of the manufacturer.

Newoldstock, just curious and out if learning what would a really heavy piston indicate? Would imagine its strong but that's more weight to more so I imagine lower rpm ability as there's more weight for the engine to chug around.

What else, just curious? Thanks!
 
Newoldstock

Newoldstock

New Member
#16
#16
philbo said:
Aha. Gotcha. 160 clone. I see some Honda 160,196,200 engines going for like $100-$150. They look pricey figuring a new predator 212 goes for like $99 on sale at harbor freight. Just wondering if he Honda quality is worth the extrat price.

Figure 6.5hp is the same regardless if the engine make. Figure if hey advertise 6.5hp that it makes 6.5hp regardless of the manufacturer.

Newoldstock, just curious and out if learning what would a really heavy piston indicate? Would imagine its strong but that's more weight to more so I imagine lower rpm ability as there's more weight for the engine to chug around.

What else, just curious? Thanks!
Click to expand...

Honda does not make a 200cc only the 196.
A 160 has a different piston but the bore is the same as the 200.
The difference is the longer piston skirt and shorter stroke ( both use he same rod ).

Owing to the longer piston it may be you have a heavy one too.
This weight will cause more vibration than lighter one ( hard to balance everything to perfection ).

Look here see the difference?

Now some GX160 Honda engines use a short skirt piston.
The Z4M piston is a good example and this is lighter than the standard dish 160 or the 200.
 
philbo

philbo

New Member
#18
#18
Ok. I popped open the crankcase and the oil coming out was not what I expected. Kinda had a milky residue to it despite changing the oil twice with less than an hour run time on it. Weird. Not like its getting antifreeze mixed in with it or something but there is nothing to mix with the oil.

Also I found 3 broken plastic pieces and a washer that has a particular pattern on it. I wonder where it goes???

The governor itself seems to wobble when I move it around while its still on the shaft. I wonder if the broken plastic pieces are from the part of the governor that rides on the shaft? Anyway, I think I'll remove it since it seems wobbly and it may be where the vibration is coming from. Besides I don't have the linkage for the governor. As they say, when in Rome... Might as well since the crank is open.

 
philbo

philbo

New Member
#20
#20
Hi buckeye! Thanks for the quick reply!

Sorry, confused. You think the governor is causing the vibration or do you think the little broken pieces are from the governor.

Sorry. I'm a little dense. Didn't get much sleep. But then Again I dunno if that matters. :laugh: :laugh:
 
You must log in or register to reply here.
Top