New to bikes, engine running poorly.

Hello, I'm new here and new to motorcycling. Recently came into possession of an 85' 750 maxim-x (canada) figured it would be a fun project to learn on. I'm an electrical technician on a wind farm, so while I'm not completely clueless, carberated engines are not my forté.

I managed to get the bike running, after doing some minor things. The bike starts easy and idles fine. If I leave the choke engaged it will eventually ramp up to a high idle of around 4k rpm, as I understand that is normal. While in the high idle, the bike sounds great, and runs smooth. However if I remove the choke, and try to apply any throttle the bike sounds terrible, almost like its misfiring, and will sometimes even stall out at 2kish.

How can it run smooth at 4k with choke but sounds like it wants to die with a little throttle? One of the needle jets clogged?

 

The problem might be your religion. May I humbly invite you to join the church of clean?

 

The choke (actually an enricher) is a seperate set of fuel passages that supplements the idle mixture. If the idle jets or passages are dirty or clogged that will be masked when the choke is applied.

While this is not a guarenteed fix for your problem, a simple and relatively inexpensive first step for someone who has never worked on a carburetor is to buy a can of Seafoam and follow the directions on the bottle for adding it to the gasoline. If the idle jets are flowing at least some fuel the Seafoam will gradually clean the crud out. You should notice a difference after the first tankful of fuel if not before.

While you're doing that, hae a good read.
The Information Overload Hour

 

Not yet. But eventually.

OP, this is what Jake750 is talking about
IN THE CHURCH OF CLEAN

 

An alternative to Seafoam is Berryman's B-12 Chemtool : https://www.berrymanproducts.com/pr...-carburetor-fuel-system-and-injector-cleaner/
Seafoam has be difficult to find in my area lately.

Just to quickly elaborate on what @k-moe is saying:

The carbs on these bikes have three circuits - three paths by which fuel/air can make it to the engine. There is the enrichment (a.k.a. "choke") circuit, the pilot circuit, and the main circuit.
Enrichment circuit - manually controlled by the "choke" lever. This circuit is used to enrichen (add more fuel) to the mixture to make starting and running a cold engine easier.
Pilot circuit - This the primary source for low-RPM fuel/air supply.
Main circuit - This kicks in at higher RPMs.

So if the pilot circuit is clogged or otherwise not working correctly, then that can be masked by the enrichment circuit providing the extra fuel that the pilot circuit is *supposed* to be providing. Which sounds like what you are describing.

There is also an adjustment on the pilot circuit to adjust the fuel/air mixture (rich/lean). If the pilot adjustment was severely lean, then that would be just like having clogged pilot jets.

 

I am suspicious that Berryman's Chemtool is what fried my carb diaphragms

 

How did you get fuel up onto the diaphragms??

 

I am not sure. I just assumed that some atomized gas would find its way up to the diaphragms. The diaphragms were probably bad before but they were absolutely FUBAR after.

 

I can't imagine any type of solvent being real good for the diaphragms....

 

I typed that weird. What I meant was that I assume some the atomized gas found its way to the diaphragms somehow.

 

Wow, thanks everyone, I'll start reading. I noticed some rust in the bottom of the fuel tank, so I have it set aside for now until I figure out what to do there, and I'll run some seafoam and gas through the bike with a temporary setup and see what happens.
I guess I didnt think about the idle jets because it seemed to idle fine without choke. But between those or the pilot jets makes sense as it really isnt happy between 1-3k.

I should definitely learn more before I get too deep.

 

Was there a fuel filter installed?

 

Neither can happen.

 

Add an inline fuel filter as insurance. It may be that rust and crud is what got into the pilot jets, but usually that also clogs up the enrichment jets as well.
HOW TO: Install a fuel filter

@chacal is out go-to for parts, but a fuel filter is pretty easy to get locally. make sure that it looks like the one pictured in the thread. There are metal bodied filters of that size (which I prefer) available on Ebay and Alibaba, but shipping usually takes a few weeks. The plastic ones work just fine though. Make sure to inspect it every year as they can deteriorate.

 

So, it had a fuel filter on, just one of those small flat ones youd see on a lawnmower. I replaced it yesterday with another small crappy one as that's all they had at my local store, but I do plan on putting a better one on eventually.
I just pulled the spark plugs out of curiosity and 3 of 4 look really good, no gunk or discoloration. The 4th was much lighter, looking at a reference chart I'd say it was too hot. Would it be safe to assume the correspondong carberator would be the one having clogging issues, running too lean and getting hot? Or would that be a seperate more chronic issue as the bike has only ran for 10 min in the last year.

 

THAT is the most likely source of the problem, and at the very least is making any other issue worse. Paper filters, especially the flat kind that are meant for lawnmowers, do not flow enough fuel to keep the fuel level in the float bowls where they need to be when under load.

Photos of the plugs would be helpful. Number them from 1-4, and place them on a neutral background.

 

I did snap a pic of the bad one, will grab the rest next time though. Wouldnt a restrictive filter affect it with choke on as well though?
Sorry, I can take a better picture eventually as well

 

That is super lean. Focus on that carb.
A restrictive filter would make it run richer than intended. No filter (or a high-flow filter) would make it run leaner.

 

Gap? Looks like the electrode post is worn away to the insulator. NG.

 

Gap was ok, the bike had iridium plugs with the pointed electrode so it's hard to see in the picture.
I'm changing the plugs and going to run 25% seafoam in it, then I'll check the plugs again after. If it's still rough I suppose I'll be learning more about the inside of the carb.
Also, does anyone have an opinion on k&n air filters? The seal around this one is junk and I dont think I want to buy another, rather go closer to OEM.

 

I have one in my X, from the PO. It needed to be oiled but I think it lets a bit more air volume than is needed pass through. The bike seems to run OK without re-jetting so I guess I am lucky. You could probably find some weather stripping at a hardware store to replace the seal with.

 

Well.... I messed with the pilot screws, by seeing how close to seated they were and then returning them to where I found them. The carb with the coensiding plug that looked bad was way closer to fully closed than the others, basically only 3/4 turn open. So I opened it up to around what the others were to see what would happen. And it sounded much better and I could actually use throttle input and it sounded pretty smooth.
BUT
I let it idle for a while, still running seafoam through it, once it got up to temperature I gave it a little gas and she started to smoke through the front of the motor, she bogged down and died. (I didn't put THAT much seafoam in) Now it will idle but any choke or gas and shes dead, with smoke from under the headers. I'm assuming head gasket. Am I effed?
The bike was basically a free barn find from a friend, I was hoping to maybe get it running and learn a little bit, but I'm not sure if I could do a head gasket, and there is lots of rust on the headers and x pipe so no way I could get those back on without replacing them. Wasnt looking to put too much money into this.

Should I just go back to peddle bikes with my 5 year old?

 

Set all the mixture screws to 2.5 turns out and do a running sync.
If you're close to Waterloo I can help you with that.
If that doesn't do it then the carbs need to be opened up, you can do that.

The fact that it is able to idle now tells me it just needs some proper adjustments and no where in this thread is that discussed.

 

If you are close to Tillsonburg. I can lend a hand.

 

The smoke could be from accumulated oil/grease on the exhaust pipes...

 

Smoke from under the headers? Is this oil burning off or compression gasses leaking out? Kind of important.
How long did you let it run? Again important.
Re the fuel filter thing - as @k-moe said lawnmower ones are no good, but I'll say that for running it stationary it wouldn't cause any issues. Question is though, how much crud got into the carbs before you fitted it?
More than likely they need a clean. I don't follow the ethos of "church of clean" and all it entails, just clean the float bowls, starter enrichner jets, and idle jets and passages -ie don't break the rack, save that for another day. You can bench synch using the progression holes while they're off.
99% of issues with these bikes is carbs, or people not re-assembling them right. And if the bike won't take throttle, and it isn't chucking black smoke out the exhaust, it's a fuel starvation issue - back to carbs again.
If the carbs are clean, bench synched, float levels near correct, the bike will run, idle and take throttle. Then you do a running sync, mixture and idle set. If the idle is erratic, fails to come down, varies wildly, then you need throttle shaft seals - "church of clean".
Just my own opinion of course.

 

Thanks for the replies again, I'm back to work this week so won't be back into it until this weekend. Not sure if I can upload a video but maybe I can try and get a good look at everything and show you.
After playing with the pilot screw on the one carb it was definitely running and idling ok. Sounded pretty decent with choke at 4k rpm, didnt stutter or anything. But I left it idling for 10 minutes or more, running seafoam through it, and when it was was up to temperature (mid way on the gauge) I gave it a blip of throttle, some smoke came out from around the headers, it bogged down and died. Now it's running poorly again, and any extra fueling (choke or throttle) will kill it with smoke. I dont think it's just dirty headers, they arent that dirty, and there was talk of a possible head gasket from they guy that had it before.

Looking at it more though, I think I could do it, might as well learn and check valve clearances and all that while I'm at it as a winter project, I should have most of the tools available to me anyway.

You guys are all awesome by the way, the willingness to help and share input is incredible.

 

The head gasket on my radian 600 was blown when I bought it. There was a small constant leak of oil from in between the cylinder and head on the left of the exhaust side. Check to see if you have and oil dripping or leaking. Might help in diagnosing.