03 engine mods

[rtboone]

I'm looking for suggestions that anyone might have about modifying an 03 engine to Super Combat specs. I'm just wanting to know if this would be something that would work with interchangeable parts ( head,cylinder.piston etc.) or requiring modification of the stock parts.

Tom

[racerclam]

Well the cylinder is a good starting point since the exaust port height gives you the opportunity to taylor the porting to what you want , you may want to make more torque a bit lower in the rpm range. The rod will have to be changed to the SC rod so the correct piston can be used . The clutch cage should be changed to accomodate the extra plate. The reed valve is the same but you will have to replace the carb rubber to use the larger carb. There are other things to discuss as well.

Rich

[Bullfrog]

My own personal preferences would suggest that it would be at least a slight affront to the Hodaka spirits to take the best, most civilized and all-round trail and trials cylinder of the various 125cc cylinders . . . and turn it into a fire breathing racer. If any choice is available to you, it would be better to start with a Combat Wombat or Super Combat cylinder. Since there is no way to make the Combat Wombat or Super Combat cylinder perform like the 03 cylinder can . . . it seems a shame to "sacrifice" (literally) the 03 cylinder in that way. (REPEAT - that's just my take on it.)

Will the 03 bottom end/primary kick and transmission stand up to full bore race treatment of the top end?

Ed

[rtboone]

Thanks for the input and I surely wouldn't want to anger the "Hodaka spirits" any more than I already have.

My aim is to build a non, or barely street legal cross country bike based on the 03 with some power upgrades.
I like having the primary kick, but if the SC top end would be too much for those parts, how about if I were to use the stock 03 cylinder with a SC head, or a SC cylinder with a stock 03 head? Would either of these combinations make sense and be more reliable? Maybe the best way to go would be to use all stock 03 parts and just add a pipe.

As of now, I only have access to an 03 bottom end, and am just fishing for ideas on what would I should be looking for in obtaining the top end parts.
Of course, I realize that sourcing some of these parts might be a bit of a challenge.

Tom

[BrianZ]

Heads and cylinders don't mix very well. Although I don't have any experience with the 03 engine, I suspect that an 03 cylinder with SC head would result in too much compression, with the resultant pre-ignition problems. The mild mannered dual sport Hodakas had a lower exhaust port than their much peakier racing cousins. This lower exhaust port means that as the piston is rising in the cylinder, it travels past (and closes) the exhaust port sooner. Once the exhaust port is closed compression begins, and since the piston has more distance to travel before TDC, there is higher compression pressure. For this reason the 03 has a higher cylinder head volume (compared to the SC), in order to keep compression pressure within a workable limit.

If you raise the exhaust port in an 03 engine, you will need a smaller head volume to regain the lost compression, and in this case you could use a SC (or CW) head.

If decide you want to play with the porting, Rich knows more about what can be done than most people.

Brian

[racerclam]

The bottom end of the 03 will also provide you with a desirable wide ratio gear box and the durability will depend on how much of an animal you are . If you ride it kindly you shouldnt have any problem . And I suggest beginning with the 03 cylinder for reasons I mentioned before , you will be able to make a more pleaurable rider from it , I can make a torque monster from that by modifying all the ports , equilizing transfer heights and redirecting the rear of thier exit as well as increasing thier volume which add more torque every where without making it pipey , as some believe. That comes fromtransfer port and exaust port height changes.Also adding a case port will really boost bottom and mid performance.

Rich

[rtboone]

Thanks Rich

My shopping list is as follows: 1- 03 cylinder @ head
2- SC rod @ piston
3- 32mm carb @ rubber manifold
4- Cylinder porting (do you have an estimate for this work?)

You mentioned the need for an extra clutch plate and different clutch cage. Would that be the cage from the SC as well ?

Have I missed anything?

Tom

[racerclam]

Tom Its best to give me a call to talk about this project in depth 702-858-9177

Rich

[eichco1]

The 03 Wombat used two different transmissions. The early trans had a second gear very close to first, and a larger gap from third to fourth. Starting with engine number Q-15501, gears 2,3,4 were changed to space out the ratios better. I would use a later model trans for a project like you mentioned. The 03 gears are also specific to the 03 and model 82. Some of the gears are wider than earlier models which may have been to beef it up. The primary kick gear seems to be a weak point, but I think some have had them hardened to make them more durable. I have a 03 I have used for AHRMA Cross Country. I have had no problems with the transmission. I have broken a couple 97/98 trans though.

The clutch cages are the same for the model 95/97/98/03. The difference is in the steel/friction plates, and the springs. The 03 used 4 friction and 5 steel, while the 97 used 5 friction and 4 steel. The 03 used a single spring in the clutch. The 97/98 used double springs.

Mark in Illinois
#492

[rtboone]

Thanks for the info.

The bottom end that I have is serial #Q15041, so I will try to find a later trans. if possible.

I was wondering about the clutch as well. I'm assuming that the parts are interchangeable so that a needed upgrade would not be to hard to install.

Tom