Engine lugging?

Discussion in '4-Stroke Engines' started by BigDaddyT, Aug 21, 2008.

  1. BigDaddyT

    BigDaddyT Member

    So now Ive had this engine about a week and have a little experience on it Im curious. I come from a diesel background and lugging is very bad. Some of the hills I pull are 4-8% and a mile long. Does lugging these cause any damage? Also at some point if the hill pulls you out of the torque curve and you drop below a certain mph are you sposed to disengage the engine to keep clutch slippage down? How long are these clutches expected to last?

    I tried to go up a mountain trail. With what I assume is a 10mph min. speed and loose gravel and rocks it didnt go well. Nuvinci or nothing im thinking. Could drop that 10mph down to 3.5 and make it a lot more doable. Any other suggestions or possibilities? The more you add into a system the less reliable it becomes so I was leary of the nuvinci.

  2. Esteban

    Esteban Active Member

    I would say that " lugging" is not good for it. If we are in a car or truck,, diesel or gas powered,, we can change gears to prevent this. The best way on a motorred bike, is to assist with pedalling. I don't think you will be pleased with any set-up trying to ride rough/steep trails.
  3. BigDaddyT

    BigDaddyT Member

    Yeah, I assist on every hill definitely helps keep the engine at peak torque.

    Any idea what mph the clutch will start to slip?
  4. WU7X

    WU7X New Member


    Do you have a multi-speed bike? I downshift until I feel the lugging disappear. of course, my speed drops, but I still get up the hill. i know that won't help if you're on a single speed.....

    I think you have a Robin/Subaru engine, right? Have you ordered the lower gear for your clutch. I did that. It dropped my top speed by maybe 2 mph, down to 26-27 mph. But much improved on uphill work for engine.

    BTW, I read your comments about gas in oil. I may have the same problem. I'm going to check it out tomorrow. Haven't been on the bike for a couple of days because of mucho rain here. hopefully can try it again tomorrow.

    Dale WU7X
  5. BigDaddyT

    BigDaddyT Member

    My top speed is 24mph Id like to get it up to 30. Im disabled but im still in decent shape. Id like to get my average speed up to 25.
    Engine still stumbles at the top of long pulls and now I have a tip in stumble.
  6. Irish John

    Irish John Guest

    I'm presuming it's a rack mounted kit. Is it a Staton with a Subaru. Your gearing is too high for the hill. Either a larger sprocket or a larger engine but I've heard reports here that the staon NuVinci will climb anything a horse can get up so that is probably your answer plus dual suspension.
  7. BigDaddyT

    BigDaddyT Member

    Its a staton rack mount with a subaru. Im going to get a tanaka 40 gebe kit but wanted something that would get better mileage. It still pulls the hills at 17-18 mph with me assisting so im thinking the gearing is ok. I want a smaller sprocket to get it up to 30mph top speed. I do run the engine at full throttle and lug it but I dont think it would not lug even if I went down a sprocket size.
    The miss or stumble usually happens near the crest so Im past the steep part. Im a little perplexed as to what would cause that. Im gonna change the plug and see if the tip in stumble goes away. These problems so far are very minor but I would like to get it dialed in and running perfect.
  8. BigDaddyT

    BigDaddyT Member

    Noticed another issue. I had heard the idle getting real low coming down the 1 mile hill but today it finally stalled and I had to pull it 3 or 4 times to start it even though it was at full operating temp. I read about these guys in Arizona having problems from the heat I wonder if Im suffering from the opposite. The air here is very cool and Im near sea level so the charge is very dense compared to other places. Id say it was about 55 degrees on the way home. On my 2 stroke I know we rejet for different temps and altitudes but this carb is supposed to be tuned to run anywhere? If it is the temp it will become more pronounced over the next month.
  9. Mountainman

    Mountainman Active Member

    getting to know my Subaru 33cc
    also get's stressed on climbs - noise that's hard to explain
    peddal harder - mainly because - THAT SOUND CAN'T BE GOOD !!

    like to figure it out - but - still running strong..

    Ride That Thing - Mountainman
  10. BigDaddyT

    BigDaddyT Member

    I didnt have the tip in problem at all yesterday. Starting to wonder if she is picky about fuel quality. I been getting my fuel at 2 different places.
  11. Irish John

    Irish John Guest

    Sounds like you are on your way to answering the problem. Keep us posted when you sort it out. If it didn't happen yesterday then it must be either fuel or spark problems. I doubt Staton would sell you a kit that runs as you describe because of being underpowered.
  12. BigDaddyT

    BigDaddyT Member

    I wouldnt say underpowered perse. My bodyweight definitely affects the performance but Im still pulling 18mph on 4-6% long hill pulls. Seeings how the top speed is only 24 mph anyways its only pulling it down about 4mph. When I say lugging Im going by the vehicle towing definition. If you are going up a hill and give it more throttle, like going 3/4 to wot, and your vehicle does not accelerate you are lugging the engine. This drives egts thru the roof on a diesel.
  13. Nuttsy

    Nuttsy Member

    Thought I had this problem solved on long climbs by keeping the spark plug clean. Ran into a head wind on a climb last week and not only did the engine lug down as you might expect, but began to -- PING!
    As in detonation. Mountainman, I think that's the odd "noise" you may be getting. I dumped the fuel tank and have been using 93 octane :-x(grrrrrrr) fuel and while the engine still gets bogged down and loses speed, again, as can be expected on a long steep climb, NO PING! The manual claims "regular gasoline" but does that mean regular as compared to premium or regular as in not diesel; or biofuel; or some other type??? The manual gives no octane rating or summer vs. winter fuel, etc. But if 93 oct. gets the job done, I guess I'll live with it. I don't want to screw up my motor from even a temporary pinging condition.
    Try it and see what it does for you.
    Also, I removed the woven paper(?) element from my air filter and soaked the foam one in K&N filter oil and squished it out. Seems to have helped the engine breathe better. Too early to tell yet. I wouldn't recommend this in a dusty, dirty environment. I ride only on clean(HA!) paved roads.
  14. sparky

    sparky Active Member

    I'm starting to regret my Subaru purchase. Two threads are talking about gas in oil, carbon fouled plugs, lack of uphill power... and even with 93 octane gas!

    I'd suspect a new spark plug would help a lot if you haven't changed it in a while.

    Looks like my 2-stroke is staying on here for a bit longer. I've really got no complaints other than not being able to fill up directly at the pump... but it's not that serious enough for me to change engines right now.
  15. BigDaddyT

    BigDaddyT Member

    I bought the subaru with the full intention of also getting a tanaka 40 gebe. You will have parasitic losses with the gear box but I wouldnt go so far as to say it is underpowered even with my weight. When I approach a hill it pulls it off peak hp down to peak torque. This is exactly what I expected. Truckers like to call that torque backup and as long as you dont fall below peak torque no harm no foul. Lugging is a matter of gearing. In a vehicle you would downshift to a gear that you would be able to accelerate in. On a one speed this is a bit problematic because there is no other gear to shift to. I think even if I doubled my hp that I would likely lug on the same hills. Only way to know is when I get my gebe. The gebe should have more than double the hp where the rubber meets the road so it will be a great way to see if this subaru just doesnt have the ghusto. My computer is dieing so I might have to replace that first so I might have to push the gebe back til next spring. This is a gamer computer so its gonna be spensive to replace.

    I havent had anymore problems with fuel in the oil. Plug is tan just like its supposed to be. The idle characteristics are great somedays and not so great some days. On real long downhills it has stalled. Im thinking the stumble might have to do with the oscillation in the gearbox. It loads and unloads the engine over and over. Its a very minor nuisance and I have seen detonatortuning bring it up in his thread. When I reach the crest of the hill it seems there is a moment where it loads the engine more as the momentum/load shifts. I let off the throttle for a sec and the loading smooths out and off I go.