Black spring vs. sprocket adapter vs. jackshaft

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Dave.

Member
#1
#1
I couldn't stand making one boy watch the other riding, so I caved and bought a DB w/97cc. The little guy is a small 10yr old. No way he can handle the 212cc on the Sensation--I always ride with him. He can handle the DB with the 97cc just fine on his own, though.

Older boy (almost 13) also likes the DB for off-road, so another reason for not putting on a larger engine: I don't need him hitting a pine tree.

But really, this DB is a dog, with the startup chugging. I don't want to spend a lot of money. I have read a LOT of threads. But none really compare the options.

1) Swap the clutch spring for a black one. Cost = 14 plus a pair of snap ring pliers.

2) Sprocket adapter and 78? tooth split sprocket. Higher cost and might limit off-road (wooded area, pine needles). 78 vs. 70 doesn't seem like that much improvement.

3) Jackshaft from Brad. Highest cost, but high quality. About as much as I paid for the DB.

I'm going to add a hydraulic brake, too, since the younger boy is taking a long time to slow down (grip strength?)

Does #3 solve everything? Would it still need #1?

Will #1 get us past the chug-chug problem? Would #2 help it out that much?

The DB is plenty fast enough. I turned out the throttle limit a little and it barely tips 27mph according to Mr. Garmin.
 
vwfan79

vwfan79

Active Member
#2
#2
The black spring won't help much, the split sprocker will help with the low end but cause you to loss top end so it will no longer do 27 mph, the jackshaft setup will give you the best of both worlds and can be used on a 6.5 hp motor when your ready to up grade.
 
C

Camjamsdad

Active Member
#3
#3
The jackshaft really wakes up the stock 97cc. If you're on a budget try hunting the for sale section. Post a want ad. They come up from time to time.
 
D

Dave.

Member
#4
#4
Hmm, ok. I was hoping that the black spring would make a decent improvement but it sounds like it might not. Then it would be the adapter & sprocket and finally probably the jackshaft anyway.

I don't want a 212 on this mini. The 212 on the Sensation is fun, but it is very right-side heavy and just feels big overall. I'd rather have the lighter engine and easier-to-handle bike.

I've not seen any used PMR jackshafts for sale for a while. I missed a DB on CL that already had one, grrr.
 
roccosbike

roccosbike

#5
#5
The Black spring is too much for that little motor, you could revv that motor wide open and the clutch shoes would never grab if you installed one.The stall on the Black spring is higher in RPM than that motor can do.Just my 2 cents.
 
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chazdaddy

New Member
#6
#6
I have DB30 (gave to grandson) that has black spring, sprocket adapter, and 78 tooth sprocket. Will hit 30mph on the street (takes awhile to get there), and is pretty fun riding in yard (1 acre lot).

I have another with black spring and pocket bike tires. With the smaller diameter tires has same gear ratio as OEM tires with 78 tooth sprocket. Really rides nice on street, but way too bumpy for offroad.

Have another with blackspring, jackshaft, and rejetted carb. The jackshaft is the way to go if you have $'s. You don't need the sprocket adapter, you can get just about any gearing you want just changing out jackshaft gears which are pretty cheap. I have it geared 13/17 and it hits 26mph at 5000rpm. I have some land I ride it on and it's about as fast as I want to go. I weight 180, a kid less than 100 would be really fast on it if they would give it the gas.

All my 97cc engines are stock with governor installed and set for approx 5000rpms. I know not many like them, but it's a great little engine IMO. Can be tuned to run very well for a kid, but If you weight 240#'s it's not going to work. Offroad, the 97cc is all I want. Street riding I like 5hp, but have 3.75hp Briggs FH that runs pretty great too.

You don't need hydraulic brakes IMO, unless you are riding on the street. When you go to larger engine 5hp, 6.5hp etc you will probably need the hydraulic brakes. I have DB30 with 5hp Briggs FH, pocket bike tires, sprocket adapter, and hydraulic brakes for street riding only (will do 40mph easy). I wouldn't ride it without hydraulic brakes.

The OEM manual brakes when adjusted properly work very well IMO, but need maintenance. The pads wear out and need to be replaced. There is an adjustment for the outside pad, another adjustment for the inside pad, and you adjust both pads by cable length. If they are not working well, they probably need some attention.
 
roccosbike

roccosbike

#7
#7
chazdaddy said:
I have DB30 (gave to grandson) that has black spring, sprocket adapter, and 78 tooth sprocket. Will hit 30mph on the street (takes awhile to get there), and is pretty fun riding in yard (1 acre lot).

I have another with black spring and pocket bike tires. With the smaller diameter tires has same gear ratio as OEM tires with 78 tooth sprocket. Really rides nice on street, but way too bumpy for offroad.

Have another with blackspring, jackshaft, and rejetted carb. The jackshaft is the way to go if you have $'s. You don't need the sprocket adapter, you can get just about any gearing you want just changing out jackshaft gears which are pretty cheap. I have it geared 13/17 and it hits 26mph at 5000rpm. I have some land I ride it on and it's about as fast as I want to go. I weight 180, a kid less than 100 would be really fast on it if they would give it the gas.

All my 97cc engines are stock with governor installed and set for approx 5000rpms. I know not many like them, but it's a great little engine IMO. Can be tuned to run very well for a kid, but If you weight 240#'s it's not going to work. Offroad, the 97cc is all I want. Street riding I like 5hp, but have 3.75hp Briggs FH that runs pretty great too.

You don't need hydraulic brakes IMO, unless you are riding on the street. When you go to larger engine 5hp, 6.5hp etc you will probably need the hydraulic brakes. I have DB30 with 5hp Briggs FH, pocket bike tires, sprocket adapter, and hydraulic brakes for street riding only (will do 40mph easy). I wouldn't ride it without hydraulic brakes.

The OEM manual brakes when adjusted properly work very well IMO, but need maintenance. The pads wear out and need to be replaced. There is an adjustment for the outside pad, another adjustment for the inside pad, and you adjust both pads by cable length. If they are not working well, they probably need some attention.
Click to expand...
If you have one revving that high than you have completely defeated the governor.
 
D

Dave.

Member
#8
#8
Really great actual-use info, thanks Chazdaddy. I see you are in Dallas. That may be more flat than we are here in Raleigh. I think I will bite the bullet and buy the jackshaft. Seems to have the best flexibility and reuse/resell options. About twice the cost of adapter-plus-sprocket, but will take care of the issue once and for all.

The kids mostly ride on the street. I've "adjusted" (messed with) the cable brake and the younger boy still can't stop it that well. It does appear to be lined up, functioning, and not dragging. Works better if I -don't- leave the extra slack the manual recommends. Best part of this one is the wife is on board for hydraulic brake (safer for the kids). Still rather have the scrub...

I didn't know that the RPMs could go to 5000 on the 97cc without taking off the governor (which I'm not going to do). I have no idea what the top-end RPM actually is, but backing out the calculation from 27MPH gives me 3900-4000, and the throttle stop can be turned out a bit more yet.

I spoke with Brad (ProMod). He was very helpful and suggested if I wanted to further improve on the JS, the -green- spring would be better for the DB, especially if the present clutch is old. He also said the black spring might cause premature clutch wear if the rider does a lot of putt-putting (like my younger boy is doing now).

Any engine swap adds up quick when that plus new clutch and mounting plate are considered. I have a spare engine (79cc 2.5hp HF Greyhound) which I guess could be used in a pinch if the 97cc goes. The 6.5 is bigger than I would want on this bike, anyway.
 
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chazdaddy

New Member
#9
#9
I have digatron tach I use on mine, so I know rpms. I concur you are at approx 27mph at 4000 rpms with OEM gearing/ tires.

Don't think I need to tell you, but don't remove the governor, plus you don't need too. I have never removed one, but there are several posts describing how 97cc without governor will turn 7000 plus rpms and throw the rod.

There are also many recommendations to remove the governor screw. All my engines will turn 5000 with the governor screw installed but turned out almost all the way. The governor works very well, I can adjust max rpms by just turning in/ out the governor screw and change rpms by just 100 rpms.

With the governor screw removed, based upon my experience, the 97cc will turn well over 5000. So, I guess there are a bunch of 97cc's out there turning well over 5000 rpms. Of course, all depends on spring between governor arm and throttle linkage. If you replace the stock spring with a stronger spring or paperclip, you have bypassed the governor, not something I would do.

The idle is sensitive to the governor spring. You will have to play with it to get the best adjustment, but the governor spring should be set to keep the carb closed so you can adjust the idle with the carb idle screw. Describing this adjustment could take awhile, took me about 1 year to figure it out, so I will leave it at that.

Most 97cc's I see are set to idle too fast because of clutch and carb issues. With the black spring installed, mine idles nice at 1500 rpms or less, and takes off at approx 3000 rpms. At idle, if I p/up the back of the bike the rear wheel doesn't turn from the engine. I can turn the back wheel with my hand and it spins freely. The engine will sound different too, no clanging, rattles, etc.

Mine sound like 5hp Briggs FH, nice to the ear. I will do a vid of mine idling sometime, but have to get wife to help. These engines are Honda clone G100 flatheads, a very well designed engine IMO, but no longer manufactured by Honda.

You will like the jackshaft, a very nice piece, and worth the $'s. :thumbsup:

Hope you have fun, I have really enjoyed playing with mine.
 
D

Dave.

Member
#10
#10
Jackshaft is ordered

I pulled the trigger on the JS, brake, and green spring. So that all cost more than the DB itself. Sigh. Thought I learned my lesson with the first mini. Oh well, I did manage to stay away for more than a year...

I'm going to have some work to do on the carb, Chaz. Even after it's warmed up, it will try to die if I give it a little gas. I have to goose it good and then it won't die. Don't recall it doing that when I test drove it, but he did have it good and hot by the time I arrived. Maybe I'm not warming it up enough.

I will have a good look at the linkage to understand how it works. The other old motor I have (79cc 2.5hp HF Greyhound) was missing gov linkage, so I made it up from a spring and really big paper clip. Works ok, not great. Does not rev very high. I made sure the DB had all its parts before buying it. At least I learned that much :laugh:
 
Outlaw Ace

Outlaw Ace

#11
#11
Here's how I solved the engine issue for my little girl's DB, came off a $35 edger on CL and it starts on the 1st pull even after sitting all winter year after year.

 
5horsebriggs

5horsebriggs

New Member
#12
#12
Dave. said:
I pulled the trigger on the JS, brake, and green spring. So that all cost more than the DB itself. Sigh. Thought I learned my lesson with the first mini. Oh well, I did manage to stay away for more than a year...

I'm going to have some work to do on the carb, Chaz. Even after it's warmed up, it will try to die if I give it a little gas. I have to goose it good and then it won't die. Don't recall it doing that when I test drove it, but he did have it good and hot by the time I arrived. Maybe I'm not warming it up enough.

I will have a good look at the linkage to understand how it works. The other old motor I have (79cc 2.5hp HF Greyhound) was missing gov linkage, so I made it up from a spring and really big paper clip. Works ok, not great. Does not rev very high. I made sure the DB had all its parts before buying it. At least I learned that much :laugh:
Click to expand...
will it run with the choke on? if so me and my friend lifted his back tire of the ground while it was full throttle with coke on and while holdingit open we turned the choke of and wella the prob stopped because it woulnd go with choke of
 
D

Dave.

Member
#14
#14
5horsebriggs said:
will it run with the choke on? if so me and my friend lifted his back tire of the ground while it was full throttle with coke on and while holdingit open we turned the choke of and wella the prob stopped because it woulnd go with choke of
Click to expand...
Yeah, runs a bit better with the choke on 1/3 to 1/2. Maybe not getting enough gas/partly clogged port?

I haven't had it long. Probably will pull the carb apart next rainy weekend and give it a good cleaning. I did the basic maintenance stuff already.
 
5horsebriggs

5horsebriggs

New Member
#15
#15
Dave. said:
Yeah, runs a bit better with the choke on 1/3 to 1/2. Maybe not getting enough gas/partly clogged port?

I haven't had it long. Probably will pull the carb apart next rainy weekend and give it a good cleaning. I did the basic maintenance stuff already.
Click to expand...
me and my friend didn't feel like pulling the carb of so we did that it would idle with ought choke but didn't rev with ought dieing
 
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chazdaddy

New Member
#17
#17
The carb is a common problem with 97cc. I bought several DB30's cheap because they didn't run. Clean the carb and you are only 1/2 way there, cause the jets are too small to run properly (EPA strikes again). Needing the choke 1/3 to 1/2 on is indication carb too lean.

Be careful with the black plastic idle jet. It has 2 small o-rings and the one on the bottom is easily damaged. I don't know where to get replacement o-rings, so if you damage the idle jet, may have to buy new carb.

The idle jet will clog up and the small jets at the back of the carb throat will too. I use brake cleaner with the small diameter red tube attachment. Make sure you get some spray out the small jets at the back of the carb. Be careful and wear eye protection (I sprayed brake cleaner in my eyes, not fun).

The stiffer clutch spring will help with the idle, let's the engine rev up some before the clutch engages. I like black spring better than green, but green should work OK.

Camjamsdad is right, easy to spend $'s on these. After awhile you will figure out is cheaper to buy another used one, than part by part. Then, you will end up with 5 like me LOL's. If you can get it to run right, will turn out to be very cheap entertainment. If you can't get it to run right, you will probably join the get Briggs or 6.5hp club, or just want to get rid of it.

The Briggs 3hp is a good option, but will probably need clutch, engine adaptor plate, more $'s, etc. I love the Briggs Flatheads, but at 2 to 3hp I would just as well go with 97cc, cause I already have them, and know how to make them run.

Good luck, some can never get it to run right. Seems easy for me, but I am retired and have lots of time to mess with it (just fun for me).
 
D

Dave.

Member
#19
#19
Chaz, thank you for the time you've spent on these detailed suggestions. I'm going to give a shot at cleaning up the carb. It's not too bad right now. I agree, sounds like its running lean.

I drained the gas tonight and put 93 in it (don't know what was in it). Acted exactly the same at startup, but I noticed after a good 5 min riding warmup, it's not bad. Give a little gas and it stalls a little, then picks up. I'm hoping that maybe the clutch spring is old/weak and causing some loading at low rpm. We'll see when I put in the green spring.

Anything else (like a new carb) and I'll be thinking about a new used engine, maybe from an edger like Outlaw mentioned. Keeping my eyes open on CL... I have a 5/8 12tooth clutch, and the old 2.5hp Greyhound to play with first. But yeah, another engine mounting plate, plus shipping. Someone on OldMiniBikes had templates for different engines. I'll maybe think about that. Besides cost, the mounting plate takes up vertical room.

For the second mini, I was looking for something other than a DB, but finding the older/good stuff is hard around here. There is some absolute junk that people describe as "vintage" to justify their high price. It's a money sink any way you go it seems. I put way too much money into the Sensation, but it is such a purring, powerful machine now, even if the engine isn't period.
 
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