Alright guys, some of you may have seen I've been doing some small upgrades to my 6.5 Lifan (chinese knock off) mud motor (longtail).


I've ran into a problem... First off heres the facts...

I had everything stock on the motor and it ran 8mph average. Now I'm going back and forth from 5-6mph...

Since then I've...

Replaced valve springs with 18lb springs, set clearence on exhaust valve to .002, Intake to .003.

Replaced stock flywheel with Aluminum flywheel.

Replaced stock Jet in carb with a #90 (I beleive) main jet.

Removed Govener.

New Carb.

New exhaust+header

new K and N intake.

also 8 degree timing key for flywheel.

SOME new gaskets, not all though....



So... I did all this yesterday.

Went to go run it today...

When motor is out of water (shaft and prop) The motor sounds amazing, and will rev high and everything sounds top notch (TO MY KNOWLEDGE, I"M VERY LIMITED WITH MECHANIC KNOWLEDGE...lol)

When I set the prop in the water, it bogs down... Almost like the torque is too much for it... But once I lift the motor up it revs back up no problem. Which doesn't make since right? assuming I dideverything correctly, I may not have gained HP but shouldn't have lost it!


Also side note.... I know this isn't right and need to look into it... Hoping its part of my main problem. On the pull start cord (which was replaced today with new cord and properly set) I will pull it and maybe 2 times out of 5,6, it wants to immediatly yank back! and sometimes even stop! Not good.... lol, also, it seems like the motor is "coughing" almost... Idk how to explain it... just doesn't sound "as" good... But AGAIN, once its running motor sounds pretty good to me without a load on it.

So after so research and picking some friends minds I've came to these things.... Please give me your feedback, I really want this thing running by duck season! All advice is welcomed with OPEN ARMS! lol


so this is what I've came up with...

1. Maybe I put the flywheel key in backwards and its actually causing the motor to not run forward... more like backwards....?? Maybe this explains the recoil start probblem?

2. My timing is off on my valves, when I changed the springs??? )If it is this would I be better off taking it to a small motor shop and having them set the timing, would it be my best bet?)

3. Something to do with the jet with the carb (I don't think this is the case)



Also, for the guys thinking about mentioning the bowl on carb being stuck, I checked it and its got enough room with the bowl to open correctly... so I know its not this....


Even if your not sure about the problem could you please give me your thought on how serious the problem is? I'm HOPING, that I at least got the motor running and worst case its just slower.... So sounds like to me, maybe its not "too" serious? I'm crossing my fingers...


again I appreciate ALL feedback, I'm doing this all on a limited budget and a limited knowledge on motors... I did this partially to learn, so I'm open to anything, I don't know much so even reccomend the small things too!

Thanks guys and god bless!

Where did you get the specs on valve lash?? We run the 35's lash at 5-7 thou.

I'm not sure, I just know that if mine were set at that, it would cause problems. You should do a little research, because lash is very important to a good running engine.

Do a leak down test.

Just take it to a lawn mower shop and ask em to look at it.

Well, I'm saying that so you don't screw anything up

The exhaust valve is on the side of the head that the exhaust comes out of, the intake valve is on the side that the intake bolts to.

If you are having a power loss and it is stemming from a compression issue, the leak down test will tell you where you are losing compression.

I don't think the valve settings would mess you up that bad, but it is possible that you damaged something by setting them too tight. Fix them to the way they are supposed to be (none of us know the specs on your motor), and run it again. If you still have issues, I would say you need to try to get a leak down done.

Depends where the loss is at, if there is even a loss. If it's blow by on the valves, could be as simple as lapping the valves in, if it's blow by on the pistons, could be as bad as having to have the cylinders be honed out, replace pistons and rings...new short block, etc... Right now, I wouldn't worry too much about it. Just try not to change much of anything. Reset the valves and go from there.

I don't know anything about your motor man and have no idea what the valve settings should be. I don't think being off .001 for a few minutes would hurt anything, but I don't even know if the numbers you are using are correct.

And as far as I know, solid lifters (which is what most of these lawnmower engines use) do not "create their own gap". Do you know if your lifters are solid or hydraulic?

Lifters ride on the cam and move the push rods up and down. I doubt they are hydraulic also.

Not sure if this will help, here is a quick video of the motor running OUT of the water... again to me sounds good... But also, like I said once the prop hits a load... it bogs down and loses a good bit of hp... Heres the video..

[youtube]http://www.youtube.com/watch?v=nhHbgRG49dM[/youtube]

Before you do anything make sure you dont have a fuel problem under load, I mean not enouph fuel. If you can and if you already have not done it, while you have the boat out and you throttle up and the motor loses power try pushing the choke a little at a time to the on position while running and if you pick up power and the engine runs better you may just need to go up a jet size, maybe a size 92, but this is all trial and error. I was able to run a couple hrs like this while out fishing on my 6.5hp with the choke half on after my mods until i got the jet size right, again not sure if this is your problem though.

Give it a shot and let us know what you come up with, as I stated before my motor would seem to be running fine out of the water but under load would fall on its face. Also, about your flywheel I have read somewhere that in a marine type application the stock flywheel we be better to stick with. I know you are worried about the flywheel coming apart at high rpms and rightfully so but I think the stock honda oem flywheel can take higher rpms than the clone original that might be an option, hope u get it worked out.

What size boat do you have this on?
What are you trying to accomplish with your speed?

It's a 200 something cc motor, it won't ever be much of a speed demon.
Have you ever set valves before? How do you know you are setting them to the gap you think you are setting them to? Are you even TDC of the Compression stroke?

There are so many things you have fooled with it's hard to pinpoint what is going on.
Have you gone inside the crankcase or pulled the Cam out at any time?

Cody has an easy way of setting the valves at TDC, call him and take some notes. Much easier than putting a piece of wood in there.

When you put your cam back in did you align the timing marks?

If you get off by a couple of teeth it will run like shit, change the compression, and kick back at the recoil like you are stating.

I know you used a feeler gauge to set the valves, but if you don't have the right "feel" they can be way off. It takes time to learn the feel, But the best way I can explain how to feel is like a knife slipping through butter, you can feel some resistance but it still slides between the valve and the rocker arm without much effort.

Honestly, I'd make it stock again.

Are you setting the valves at 1/4 past TDC on the compression stroke or are you setting them one at a time on the back side of the cam? Even though some manufactures recommend 1/4 past on the comp stroke, I've found you are less likely to screw it up by setting on the backside of the cam. I always checked that way anyway, but now that is just the way I set them.

Straight TDC is fine on these motors.

It's fun to fool with these little motors and make one run, don't pull your hair out... You'll get it right.

Where are you from?

CB, first time I did do 1/4 padt TDC then someone told me "IMO" a better way... do one spring at a time, I guess that way you don't take really any chance of screwing them up or dropping them.

Woodie, I fell in love with tearing them apart and fooling around, I'm a young college kid working for the state and not saying I'm rich... But if I screw one of these little motors up, a new one cost around $100 sometimes on sell around $80... a lot better then my 10 horse 4 stroke susuki I had...

I'm currently living in the sunshine state of FL, south Fl at that... I just moved for a job and will probably be bouncing all around the state within the next year chasing advancments within my career, if not a whole other state. So to answer your question... FL for now.

welllppppp....

About to run out of ideas here....

re adjusted the valves again to exhaust .004 and intake .006, definatly made a difference, motor started after 2 pulls after choke, so that was a plus.... But still had the compression problem when prop was on a load.

So bought a bigger jet for the carb, a #92 and a aftermarket Emulsion tube.... was stoked! tryed it today and nothing changed. Out of the water, motor wants to rev, sounds great (maybe a little sputter here and there, but nothing serious) As soon as the prop hits, it loses alot of power but still pushes... Then when I try to run it WOT the motor wants to skip and putur and eventually cutt out and die. So I have to run it right under WOT and it actually runs ok. Then when I hit a clump of vergitation it reallys gives in and almost dies quite a bit.

I got 2 more ideas... Tomorrow going to exchange the aftermarket flywheel with the stock one, then give it a go?

My thinking is that when the prop hits a load its too much for the motor so it wants to die out... With some more wieght maybe it will have the "umpff" to get it going again??? idk

If that doesnt do it... Maybe one more time the next size up jet #95, new gaskets for the whole motor... then try it again, IF NOTHING.

SCREW IT, either bringing it all back to stock or going to buy a new predator, Does anyone know the measurment from the base of the engine to the horizontal drive shaft? Basically so I know if I can just re use the u joints and frame?

any input as usual is welcomed! Thanks for everything guys.

Where did you get the valve lash # from?

Normally an exhast valve needs more clearance because it will see more heat and expand more than an intake, but I am not sure what you would set them too.
Try .005 intake and .008 exhaust

The way you are saying it cuts out and dies sounds like it starves for fuel when you put it under load. Jetting up does not always solve the problem, check your plugs and see what color they are.
What size carb do you have? You sure its the right one?