Bone stock Honda GX200 6.5hp

#1
Hi there.

Going to be building up a DB 30 with a 6.5 hp genuine Honda GX200 and a Centrifugal clutch for a race series that another member on here has organized.

I would like to lightly modify this box stock GX200 with a header/muffler pipe that will fit around a DB 30 or Dirt Bug frame, richer jetting (main and emulsion tube), a velocity stack and pod air filter. I want to retain the stock governor, valve springs and fuel tank. Is this a good plan or are there better build paths to follow?

I also plan on using one of those billet adapter plates for the DB 30's to mount a clone or Honda engine as I feel they stiffen up the rather thin engine mount plate.

Let me know what you think here and if I should consider other options or upgrades.
 
#2
Sounds like you are on the right track with your engine mods, since you are going to keep your governor. Not sure if there are straightaways in your race series, but sounds like the person with the best gearing may be more successful, whoever is geared with the best mix of torque/top-speed. What clutch are you running?
 

trinik7597

Active Member
#3
Is that the deal it has to be bone stock accept for opening up the air flow ?? There are a couple little tricks you can do to the valve train to gain a little more power and still be considered stock ..
 
#5
Sounds like you are on the right track with your engine mods, since you are going to keep your governor. Not sure if there are straightaways in your race series, but sounds like the person with the best gearing may be more successful, whoever is geared with the best mix of torque/top-speed. What clutch are you running?
Yes that's a good point about topping out in the straights, that would suck lol. I'll be running a Comet or Max Torque 12t 35# clutch.

I'll also be using the stock Dirt Bug or DB 30 rear sprocket, not sure how many teeth these are, 60T perhaps?

How are those Hillard clutches btw?
 
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#6
Is that the deal it has to be bone stock accept for opening up the air flow ?? There are a couple little tricks you can do to the valve train to gain a little more power and still be considered stock ..
I believe so but not entirely sure and right on, sounds interesting!

I'd be great to learn these said tricks:wink:
 
#8
Yes that's a good point about topping out in the straights, that would suck lol. I'll be running a Comet or Max Torque 12t 35# clutch.

I'll also be using the stock Dirt Bug or DB 30 rear sprocket, not sure how many teeth these are, 60T perhaps?

How are those Hillard clutches btw?
I have yet to run my bike with the flame clutch. Weather has been rainy all week. I also ordered a new 12T driver as the one I have is used and needs replaced, waiting on that.
 
#9
I have yet to run my bike with the flame clutch. Weather has been rainy all week. I also ordered a new 12T driver as the one I have is used and needs replaced, waiting on that.
Lol...."flame clutch" They look okay but I don't like how the clutch bell is separate from the rest of the clutch assembly and how it rides directly on the engines crankshaft via bronze bushing.

I really like the Comet LA350 series cent clutches even though they share the crankshaft riding clutch bell design. You can tune the engagement RPM's.
 
#10
Lol...."flame clutch" They look okay but I don't like how the clutch bell is separate from the rest of the clutch assembly and how it rides directly on the engines crankshaft via bronze bushing.

I really like the Comet LA350 series cent clutches even though they share the crankshaft riding clutch bell design. You can tune the engagement RPM's.
LOL, yes, it does have a silly name, "The Flame, burn chit up". That is the only drawback I have seen as well. The drum is a little loose with just the bushing on bushing, but i have ordered a WMS gear that has roller bearings instead of a bushing, but still 12 tooth. I am hoping it removes a lot of the play in the drum. You can tune most clutches with a stonger/weaker spring as you can with the Comet LA350. Noram has a GE series, its a drum clutch, however the drum is roller bearing. I have the GE Clutch and it is super smooth, and no play in the drum. Typically no matter what clutch you use, it will have a busing between the drum and crank as the crank has the key way that nothing roller can ride on.

http://out2win.com/catalog/images/NADrum.jpg
Here is a picture of the roller drum from Noram that i have, but it still requires a bushing on the crankshaft.
 
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#11
Without sealed new stockers, I could foresee more cheating than college Spring Break.
IMO, the multi-adjustable "billet" plates are lame.
Bearings, brakes and tires could alter the drag a lot.
Carb bore sizes vary, as do chamber sizes, piston dish, block deck, lots of variables to "stock".
5/8 drill bit and a lifter bore hone can add a decent percentage of flow,
 
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#12
I know this thread is a bit old but there are only a few basic rules for modifying engines. (we are meeting Sunday to have everything finalized and put into print)

1) must be pull start
2) must start as nothing larger then a 6.5hp @ 212cc - (you can run anything smaller)
3) must be four stroke based on any industrial purpose engine

We don't want to make a bunch a rules and be tearing into engines to prove out cheats. This keeps it simple.

We are aware that some people might throw a ton of $$ into their engines but I doubt they will gain any huge advantages. Our track is a road course and is basically sand. It also is not flat by any means. We also want to the bikes to have stock appearing frames (no stretching, no adding suspension and they must be parallel tube/box frame types) This keeps the mini bike spirit alive and greatly reduces the handling.

It's all for fun too, no big time fame, just bragging rights... and you get to have a bad ass trophy for a few months. :thumbsup:
 
#13
Sweet man I'm excited to come out. I've been out ripping around on my newly build Dirt Bug and just got.my stage 1 kit from OMB.

You might have seen in my other post, "my first DB 30" that I added front suspension so I'll have to get another front fork lol.
 
#14
Yeah, those forks look sweet. Very tempting, but we don't want to start blurring lines between mini bike and dirt bikes. Also read your thread about the front rim offset. I just got my dirt bug last season after using a mini bike with a dirt bike front wheel, I figured the DBs just handled like :censure: or thatI wasn't used to the frame yet haha. I will be following your lead on getting a a new front rim :thumbsup: I'm actually downing some coffee ATM getting ready to head out to meet the guys to discuss all the rules in detail; should have something posted later in the week.
 
#15
If it was me I would run higher ratio 1.3 rockers, 18LB springs with the stock cam and bump the compression a little. Are you all filling up with the same fuel? Are you all limited to 87 or can you run 91? You want to limit people from modding motors a little than make every one run 87 to keep compression down and timing from being advanced to far. If I could run 91 I would run the high ratio rockers, compression and try seeing if advancing the timing adds any power on top of the basic carb and exhaust tuning. Being that your running such low RPM advancing timing might not do any thing so make a small 2* adjustment and see if it dose anything. Be extra careful if you raise compression with advancing your timing. At minimum I would take the head off, lap the valves and put it back together with a thin head gasket.
 
#16
No alcohol or methanol... This is essentially year one, we're leaving the rules a bit more open to see what works and what doesn't. Were not too concerned about big power engines since the poor handling and track conditions will make most of the power useless.
 

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