97cc DB-30 head
- Thread starter mr.modified
- Start date
- Tags 97cc db-30 head
Back for round two...
Just took the side cover off tonight for the first time since I put the welded cam in. The cam and the lifters don't seem to have any nicked up spots or scuffing on them. I noticed the other day that a few of the links in the chain were stuck on the bike. So I took the chain off and put it in some kerosene. Their not stuck too bad, just stiffened up a little. I didn't oil it much, and the damp garage must not have been too good for it. I took the exhaust off the motor and cut the muffler off. I'm going to weld on a piece of pipe about the diameter and lengh that the muffler was. This thing sounds too whimpy. The bigger pipe should give it a megaphone effect and make it a litte louder. I think i'll take the old tillotson carb back off, drain it out, and paint it. That goes with the continental quarter midget engine I'm supposed to be putting back together. I'll get an expendable carb on there and see if I can get it to run on alcohol. You would think something would have to give on this thing. If running on methanol doesn't do it, I'll have to make a super charger for it...:laugh:
Just took the side cover off tonight for the first time since I put the welded cam in. The cam and the lifters don't seem to have any nicked up spots or scuffing on them. I noticed the other day that a few of the links in the chain were stuck on the bike. So I took the chain off and put it in some kerosene. Their not stuck too bad, just stiffened up a little. I didn't oil it much, and the damp garage must not have been too good for it. I took the exhaust off the motor and cut the muffler off. I'm going to weld on a piece of pipe about the diameter and lengh that the muffler was. This thing sounds too whimpy. The bigger pipe should give it a megaphone effect and make it a litte louder. I think i'll take the old tillotson carb back off, drain it out, and paint it. That goes with the continental quarter midget engine I'm supposed to be putting back together. I'll get an expendable carb on there and see if I can get it to run on alcohol. You would think something would have to give on this thing. If running on methanol doesn't do it, I'll have to make a super charger for it...:laugh:
Got my new exhaust installed. It's considerably louder than it was with the "glass pack" muffler. Down at idle, it gives it a sort of bubbly sound, but it sounds much throatier when you step on it. So far I haven't had time to make the switch to methanol... I'll take the pipe back off and give it a quick coat of high heat black when the humidity is a little lower.
Just for informations sake, I was testing an old analog tach to see if it would work off a small engine flywheel mag, and it shows this thing reved up to 4000. I would think it would rev just a bit higher than that, but maybe there isn't quite enough voltage for the tach to work properly. It wasn't that quick to respond to rpm change and was a little jumpy. I hooked one wire to the shut-off wire and grounded the other wire. I didn't want to hook it directly to the plug wire for fear of burning up the tach, I don't know too much about them.
...I still didn't get around to switching this thing over to alcohol. I've got a beat up tecumseh 5 horse carb I was gonna try when I get a chance. I did paint the new exhaust.
...I still didn't get around to switching this thing over to alcohol. I've got a beat up tecumseh 5 horse carb I was gonna try when I get a chance. I did paint the new exhaust.
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I took the tecumseh carb off my exposed crank 8hp project and bolted it on the super stock. The throttle pulls open from the opposite side as the tillotson, so I just bolted my cable mount on the other side. But since I have the throttle return springs hooked into a small hole in the shroud, I had to make a place to hook them where the throttle cable used to be. Another scrap peice of aluminum diamond plate solved that problem. Venturi size is about the same on both carbs. But, I couldn't get it to idle or rev up. I played with the mixture for quite a while till I realized that I couldn't get my exposed crank 8 horse running with that carb either. Maybe I thought that carb was clean looking inside and never sprayed it out. I can't remember what it came off of. I tried the tillotson I just took off on the exposed crank machine and got it to stay running for a good while. I'll either clean this one out or just try a different one. Then I can try alcohol. At least I'm set up for most carbs now with the return springs on the other side.
http://www.oldminibikes.com/forum/e...c-budget-cam-project.html?highlight=97cc+head
Smoothed it out mostly with a bench grinder, then finished it off with an air powered sander/gasket cleaner.
Smoothed it out mostly with a bench grinder, then finished it off with an air powered sander/gasket cleaner.
Super stock update
Haven't been on here for a while. The Super stock is still in good running condition with the modified cam and head still installed. I took it for a few high speed trips at which I was at full throttle for most of the 8 minute run. I can't believe that is doesn't throw the rod. Last night on one of my runs I hit a puddle and the super sock air filter got saturated, killing the engine. I ripped a hole in the sock and got it going again, but 45 seconds or seconds or so up the trail was a bigger puddle which I tried to slow down for but couldn't get all the way stopped. This also killed the engine and when I was going for the pull cord, I noticed that one of the intake bolts had fallen out. Luckily, I didn't hydrolock the engine or anything. I'm going to fix up the threads for the intake and add a brace to help hold up the carb so it doesn't strip out again. I have probably run at least 6 or 7 tanks of gas through it since I put it together without any problems. It never did idle perfect though, which I think is caused by the carb being a little too big and not pulling enough fuel at low rpms/vaccum. Next weekend I hope to make a run of about 16 minutes and see if I can blow this thing up. When the rod finally goes, it'll make a nice shelf piece...
Haven't been on here for a while. The Super stock is still in good running condition with the modified cam and head still installed. I took it for a few high speed trips at which I was at full throttle for most of the 8 minute run. I can't believe that is doesn't throw the rod. Last night on one of my runs I hit a puddle and the super sock air filter got saturated, killing the engine. I ripped a hole in the sock and got it going again, but 45 seconds or seconds or so up the trail was a bigger puddle which I tried to slow down for but couldn't get all the way stopped. This also killed the engine and when I was going for the pull cord, I noticed that one of the intake bolts had fallen out. Luckily, I didn't hydrolock the engine or anything. I'm going to fix up the threads for the intake and add a brace to help hold up the carb so it doesn't strip out again. I have probably run at least 6 or 7 tanks of gas through it since I put it together without any problems. It never did idle perfect though, which I think is caused by the carb being a little too big and not pulling enough fuel at low rpms/vaccum. Next weekend I hope to make a run of about 16 minutes and see if I can blow this thing up. When the rod finally goes, it'll make a nice shelf piece...
I've got the intake threads patched back up. Maybe it's time to make the switch to methanol and run it free air without the fan, since i'm only running it at higher speeds anyway and not idling around. I was thinking maybe I could run it on 1 part alcohol, 2 parts gas and still use the same jets... just richen it up a bit.
Update on the whereabouts of the modified chinese minibike engine. After being removed from the bike frame in 2012 for repairs, I never got back to it and it eventually made it's way to a shelf full of vintage oil cans. It sat there for a couple of years until I needed the vintage tillotson carb for my briggs 3hp airplane engine. Now I've had ideas of finding a slightly smaller bore carb and finally putting it back on the minibike frame (which has also been sitting for years) and trying to finally blow this thing up. I think the tillotson was too big, never idled good. I remember I always had to keep it adjusted up pretty high for it to stay running.
Another update for laughs. It's been around a year and a half. The engine still looks about the same as it did in the last pic, except now I don't ever plan on using this in a mini bike again. Might use it for something, but for now, it's just going to be sitting where it is now, which happens to be only about 10 feet away from where it is in the previous picture above. Shame all the older pics in this thread got deleted. Been a long time I guess.
So sad, most of the original pictures have been deleted... Good thing I saved the pics of the head on my computer, plus I still have the engine in storage. Still sitting on the floor of the shop. Anyone have any experience with mini milling machines? Like the ones from harbor freight or some other better brand? I'm thinking of getting a small one to do things like this. Have more cylinder head projects planned. I've been trying to cast my own cylinder head for a briggs engine.