4-stroke engines quieter?

[Irish John]

Interesting to hear this. I just got my first bike running yesterday, powered by a Hua Sheng 49cc 4-stroke with a Hoot gb. The Hoot came with your basic funky-looking brown grease in it. I took an amalgam of advice from this site and put several ounces of gear oil in the gb (Valvoline Duro Blend 85-140 synthetic gear oil) before I took it out on the road. I've put about 4 miles on it so far, just riding around in the neighborhood, top speed 20 mph or so. GB was hot to the touch (noticed while wiping off oil that was shprootzing out of the vented plug) but I didn't take this heat as a bad sign - it's a piece of metal bolted to the engine after all. Have others of you had performance problems / equipment failures from overheating using oil in the gb? How hot should the gb feel if things are "OK"?

I think you should clean out that grease that came with the kit. The Grubee from MBB imports in Sydney has the same gelatinous stuff in it.
I can't speak for the Hoot yet cos I still haven't run it but I can speak for the Grubee. Mine ran really hot and the clutch slipped when wet. I use tacky white lithium grease and quite a lot of it. The gearbox only ever gets warm and never too hot to burn your bare leg. The white lithium grease is by far the best I've tried, 20 mph is totally hopeless for a top speed and may have something to do with a slipping clutch. The 44T sprocket is, from all I've read about the hoot, way too large just as the 56T is way too large for the Grubee. They don't make smaller sprockets so they just threw the old HT 44T in with the kit cos it's the smallest they can readily get. This indicates one obvious thing to me and that is that the people who design these kits know two fifths of nothing about how the assembly actually runs. That is why I'd ditch their grease and use my own. I use MPG lithium grease made by Rock Oil Company of Warrington in Cheshire UK. It's available from good trail bike shops.
Some other good reports about wet GBs on these pages became bad reports after a while. Some Grubee owners however have had success with a wet GbB but the secret seems to be a very small amount and not as much as you seem to imply you put in. How does it splash out if your GB is sealed with that screw that goes in the fill hole?

 

[cruiser66]

Interesting to hear this. I just got my first bike running yesterday, powered by a Hua Sheng 49cc 4-stroke with a Hoot gb. The Hoot came with your basic funky-looking brown grease in it. I took an amalgam of advice from this site and put several ounces of gear oil in the gb (Valvoline Duro Blend 85-140 synthetic gear oil) before I took it out on the road. I've put about 4 miles on it so far, just riding around in the neighborhood, top speed 20 mph or so. GB was hot to the touch (noticed while wiping off oil that was shprootzing out of the vented plug) but I didn't take this heat as a bad sign - it's a piece of metal bolted to the engine after all. Have others of you had performance problems / equipment failures from overheating using oil in the gb? How hot should the gb feel if things are "OK"?

Sounds like you are on the right track. The GB gets too hot to touch comfortably which, I believe, is normal. Oil transmits heat better than grease which is why the box feels hotter than with grease. I run about 5 ounces of 75W90 synthetic with good results. I use a mouse pad noise insulator glued to the outside of the GB. It's a great heat insulator too. I can rest my bare leg on the GB while riding with no problem. I also use an internal baffle to stop the oil "shprootzing".

66

 

[andyinchville1]

HI,

Not necessarily...;-)

Andrew

 

[Vishnu Tensleep]

thanks for the responses!

To Irish - my Hoot has a 'vented' fill screw - a little hole drilled in it. Perhaps it's not necessary if most of the space in the gb is air and there's only grease on the gears, but if you use oil there's less air and so the oil expansion from the heat can blow out your seal? At any rate that's what's on my gb, and that's where the oil is coming from. Didn't seem to happen with only about 2 oz of gear oil but I'd only gone up and down the street a few times after the engine started the first time.

To 66 - thanks for the pics and further info about the gb. I got the idea from posts by you and Happyzeds. The pic of the baffle is invauable!

To Andyinchville1 - that's a dang wild looking muffler set up. I hope it's quiet after all that.