85 Honda 200x carb issues

[racerx5467]

New to this site and hoping to find some direction on my newly purchased '85 200x. I picked this girl up about 2wks ago. When I bought it, it ran and that's about it. I've been going through it, and discovered the timing was off a tooth. (seller claims the top end was rebuilt with a 66mm top end kit) I've been doing quite a bit of research on the web, and with trying to tune the carb, I'm coming to conclusions the stock size replacement carb the previous owner purchased (24mm mikuni) isn't sufficient for the bore, as it runs at best crappy, only with the choke on. Adjustment of the air/fuel screw has little to no effect. I'm considering purchasing a mikuni 28mm carb, or perhaps increasing the main & idle jets. Any advice would be highly appreciated. As well, by going to the 28mm carb, I know I'll need the flange adapter, will it interfere with using the stock air box? I would like to keep the bike original as much as possible
Thanx in advance

[86125m]

what color is you spark plug. Because I just cant see it not getting enough fuel because of carb size as my 200m is .75 over which is just .25 smaller than you 66 mm bore and its running on the stock 22 mm carb just fine.

[Jmoozy27]

Is rejet the stocker before dropping a couple hundred on a bigger carb. To run that 28mm effectively you would need to mod the motor out a little more. Save the money for now. Use what you have, we can help. Just answer a few questions:

1. Do you know what mods are done to the motor? (Pipe, intake, cam, higher compression piston)

2. Have you taken apart the carb to see if it is clean and to see what jets are in there currently? (83-85 200x should be 38slow 105main) but not positive on that.

Until you know what you have it's hard to diagnose a solution to your problem. Throwing parts at something usually doesn't fix it. Sounds like some simple tuning will solve your problem. Post a few pics of your trike so we can know what it is for sure.

Buy a few new spark plugs so you can read the color between adjustments. A nice tan color is what you want the middle porcelain to look like.

[yaegerb]

Welcome to the site. The search feature in the upper right hand corner is your friend 

Always start with the FAS principle: Fuel, Air, Spark.

1. Fuel
An easy issue to check first is your fuel lines and your carburetor. Have you ensured that your fuel lines are unblocked (fuel flowing freely) into the carb and that you are using fresh gas? Another to-do item for these almost 30 year old machines is to rebuild the carburetor. Shindy sells very inexpensive kits on ebay for the OEM 24MM Keihin carb.
Once the carb is rebuilt……
buy a few main jet sizes from 112, 115 118. You can do so from jets R us. Start with a 118 main and go down from there. 40 pilot should be good enough. Below is the method I use to jet.

These jetting specifications are designed as a rule of thumb. They are in no way absolute. Variations in air density, specific gravity of fuel, altitude and other engine modifications play a large part in jetting. Newly built engines need rich jetting during break-in. Do not jet for power until an engine is broken-in.

Myths
1. Plug reading may/may not work.
2. Revving the engine while it’s sitting in the garage doesn’t work.

Other than Dyno testing, the steps below is the simplest way you can jet your engine.
1. Find a gentle slope that you can ride in 2nd or 3rd gear. Look for something that will put a reasonable load on the engine. This will be your “dyno”.
2. A basic outline of which jet is active at a particular throttle setting: Pilot Jet = 0 to 1/4 throttle. Needle = 1/4 to 3/4 throttle. Main Jet = 3/4 to Full Throttle. Changing the Main Jet size won’t affect how your engine idles or
runs at 1/4 throttle. Engine RPM isn’t what determines which jet is active - throttle position does.
3. Make the recommended jetting changes. Always start rich and work leaner.
4. Start and warm up the engine, then ride your ‘dyno hill’. Any point where you feel the engine stumble or hesitate indicates a tuning problem. Note the throttle position and modify the corresponding jet (1/4 to 1/2 throttle = needle. 3/4 throttle or more = main jet).
5. Only change jetting by 1 step at a time, and 1 circuit at a time (don’t change needle and main at the same time). Re-check after every change.
6. Once the engine runs smoothly throughout, you’re jetted!

If you ever notice an abrupt loss of power, or engine sounds change, shut it down.

2. Air
Almost always overlooked is the air filter unit on these machines. If you haven't already, spend the money on a quality airfilter like a UNI or a K&N. A properly oiled UNI or K&N will deliver consistent, fresh air to this machine.

3. Spark
Unscrew your sparkplug from the head, leave it in the boot and ground it to the side of the 200x head. Turn off all lights in your garage. Can you see a FAT BLUE spark? You will instantly see if you have enough spark or not. If not, then you may have an electrical issue and not enough spark to ignite your fuel. If that's the case, let us know...there are lots of good ATC electricians on this site...ahem...KBOnly...ahem.

Another item to note.....
I would also ensure that you have re-set valve lash on the machine as improperly set valves can cause erratic starting and running behaviors.

If you decide to go the 28MM Mikuni route there are tricks to do this and still use the stock airbox, but most guys give up and run pods (I strongly advise against this unless you are in a waterfree/racing environment). PM if you are serious about going that route.

[racerx5467]

Thanx for the replies! I'm new to this site and figured I woulda received a notification for the response. So here I am on a Saturday once again troubleshooting the issue and figured I'd do some reading.
Currently I'm waiting on the mailman to get here, with expectations of several jets to come. This machine no longer has the kehein carb, its one of the aftermarket mikuni carbs. I did pull the plug and the plug is still white/burnt color, indicating it's running lean. So- I ordered the next 2 main & idle jets up in size. I think I'm going in the right direction, out of boredom and the fact I was ordering larger mains anyway, I ran a fine drill thru the main to enlarge it. After reassembling, I got the trike to run, but it is now choking on too much fuel it seems.

[racerx5467]

In responset to what has been done to the machine, nothing major as far as I can tell this far. Previous owner claimed the top end was redone with just a standard (stock parts w/over size piston & bore) rebuild. For now, I've been inside the valve cover to set timing and readjust the pulse generator... (previous owner was off 2 teeth on the cam gear.) The only other mod is a full D&G exhaust. Obviously, with the last post statement, I have checked the carb even thoughi t is a new carb. I appreciate the replies.... Frustrated, but becoming more & more educated with carburetor!