inferno sports gx21 problems

[doby303uk]

hi all i have a little prob with me no car, it just doesn't feel the same anymore, a little less responsive, and it seems to have lost a little top end, the gx21 was broken by idling through a couple of tanks of fuel, then ran another tank with car on road but no full throttle. then i began to ran the car quite quickly.
I've used about a gallon of fuel, from some of the reading that I've done i feel that i may not have broken in the engine correctly?
and the engine may be lacking compression, as i red somewhere that 1 way of testing the compression of a pullstart engine is to lift the car using the pullstart and if its ok then the engine shouldn't turn but when i do it it does turn. there is a little resistance when i turn flywheel by hand.
what do you guys think have you got any suggestions for me, should i strip the engine?

also I'm thinking of getting a RBWS 2, how much of an improvement in performance (acceleration, speed) would this give twice as much?

mucho thx!

 

[RobH]

The pullstart-compression test only works on the smaller 1/10th scale cars. The 1/8th scale buggies (inferno sports is one) are so heavy that I think they may turn the engine over in some cases.

I rescently told someone else how to test from compression. Maybe these tips will help you find out if you need to rebuild or buy a new engine:

Originally posted by RobH

Here are a couple of way's I've learned to test for piston / sleeve wear.

1.) try and turn the flywheel by hand (with the glow plug installed). When you get to top dead center (tdc), it should become really hard to turn. If you push really hard, you should be able to turn it over, but it shouldn't be easy. If it turns over easy, you need an engine rebuild.

2.) since this is a stadium truck, you can do the pullstart test. put the rc on the ground and see if you can pick the rc up by the pullstart cord (with the glow plug installed). if the engine turns over and the cord spools out, the piston and sleeve are worn. I tight piston and sleeve will cause the car to lift in the air by the pullstart cord.

3.) remove the glow plug and turn the engine by hand via the flywheel. When you get close to top dead center (tdc), you should feel a "pinch" where the sleeve constricts around the piston. no pinch - no compression - time for rebuild.

4.) remove the engine (glow plug installed). hold the engine by the flywheel and put the engine close to top dead center. Then postion the head so that it's pointed at an angle, being held up by the engine compression. When you hold the engine in this way by the flywheel, it should be able to support it's weight for 3-4 seconds before flipping over TDC.

I have never owned the gx21 engine nor have I owned an RB WS7II. I can't really tell you how much more power the WS7II will have than the gx21. I do know however that the WS7II has been know to kick some major butt. If you're looking for top-end perfromace, the RB C5 is great engine too.

A tip for the next engine you own: You really should buy a temp gun. It doesn't sound like you have one. I'm guessing that you tuned the engine pretty lean (hot) and that's why you have no compression after only 5 liters of fuel. You really should be able to get 10-15 liters out of most engines if you tune them properly.

Anyway, a temp gun can tell you how hot your engine is. You can then richen the needles if it's running too hot. That will go a long way to help extend the life of your engines. A good temp for most engines is about 110-115 degrees C or 230-240 degrees F. Some racers will push their engines as high as 125 degrees C, but that's not really recommended if you want your engine to last very long.

Good Luck and Welcome to RCNT!

Cheers,
Rob

 

[doby303uk]

thank for the welcome m8

its a longtime return to an old fav hobby, was into 1/10th electric about 12 years ago and also had a stab at nitro back then but to no sucess. anyways i know what the problem is now, the motor is stripped and i can push the piston by hand past its normal operating bounds. i had a problems with starting the engine using the recommended kyosho settings, this was causing the engine to over rev for no reason, so returned to the shop the following day and the assitant noticed that the engine was set to run without the air filter. strange i thought why would i want to run the engine without the air filter ???????. anyways i think this has not helped. so off to the shop next week for new piston+liner.

i'm just begining to get head round the nitro engines again, can wait to get some tweaking done

A quick question my old irvine .21 ABC block had piston rings, never seen a mention of piston rings anywhere over the last couple weeks of returning to the scene?

would be cheaper than replacing piston and liner.

 

[GilBeQuick]

Newer 2 stroke R/C engines don't use piston rings. Instead they rely on a tapered sleeve (liner) for compression....the sleeve getting SLIGHTLY narrower toward the top. Which is what gives you that resistance when you turn your flywheel.
Check on how much a new piston and sleeve will cost you... If the cost isn't that great of a difference, you may want to upgrade to a new engine altogether for more performance.

BTW, how do you like your 7.5 Sports? Does it handle good even though it doesn't have foams?

 

[doby303uk]

i'm just getting back into the scene m8 foams (inserts)? , its feels ok to me but i havent had much chance to really run it. only run about 2ltr and its fooked , £40 all in for the piston and liner i do plan upgrade to a ws72 but that no be for another month or so. still think it was a bad idea getting rid of piston rings, more advantages mind u raises the cost of maintiance of the engine thats better for them.

man this sux £400 and 2 ltrs of fuel I'm sick, me want to play

 

[Kuma]

My father has an MP7.5 Sport, he seems to like it but I don't, I was going to replace that plastic spur gear diff with a spare Ofna MBX diff I had laying around, and the chassis has some flex so he got some alum chassis braces. The motor is fairly reliable and awkard to tune and lack of power, he also put some Ultra MBX Pro (blue) tires on in replacement of the no-foam tires. But it handles well and really floats in the air.

Doby, if all else fails, check the heatsink head screws, I've had an engine "lose" compression and turned out the head screws came loose and all is fine now, it happens.

 

[doby303uk]

thx for the advise kuma, but they were tight, i've decided to complain to Kyosho about the cars enigine and their setup instructions, if i can find somewhere to send it, here what I'm sending them what you think they'll say

After much consideration of the available 1/8th buggies on the market and my budget I recently decided to buy (11/10/2003) an Inferno MP7.5 Sports.

After reading the instructions, making sure the engine settings were correct (Needle Value, Air/Fuel Mixture, Throttle Value Adjustment Screw) and having to wait a very inpatient 17 hours for my glow starter to charge I began the braking in process.

My First problem arises here, I get engine running but have problems getting the engine to idle correctly, it would settle but then the RPM of the engine would start to rapidly increase, for no apparent reason? I would then stop the engine because of fear of over revving the engine at this stage of its life. After spending sometime and approximately 2/3rds ish of a tank of fuel I decide to phone the shop I bought the car from for some advise and if they would correct me if things were wrong.

Returning to the shop the following day, the shop assistant gets engine running and starts to encounter the same problems I was having, he then realises there is a problem with the Air/Fuel Mixture screw setting and it is set to run without the air filter? So he readjusts the Air/Fuel Mixture screw and bingo the engine is idling correctly and the problem is solved. So I return home and continue with the breaking in process, running 2 tanks of fuel with car sitting off ground idling. Then I begin to gently run the car on a flat tarmac surface, applying throttle gently, never full throttle, I do this for a further 3 tanks of fuel. For the next couple of tanks of fuel I start to run the car slightly harder with each tank of fuel. I would also let the engine cool before the next tank of fuel at all times.

Anyways approximately after 2 litres of fuel and 2 weeks later I notice something different about the car just doesn’t feel the same, there’s a loss in the cars performance, and its getting worse. I’m puzzled it can’t be the engine already, after much reading about nitro engine problems etc. I begin to think there’s a problem with the engines compression and to my surprise there is, the piston and liner are knackered. Now at first I was upset at the thought of just spending £400 and having a broken car already, but then just had to accept it. But after further reading about nitro engines, breaking in etc I feel that I have done everything correctly and think that the engine has incurred damage in the initial getting the car running. I feel the problems I encountered at the beginning are due to the set-up instructions given with the car. Why would I want to break in the engine without the air filter? , So why give me these settings?

I ended up going with a car Kyosho car on returning to the scene from a 12 year or so break. I had Kyosho cars then to (Laser ZX, Optima Custom Special) and thought they were great cars with a ready supply of spares. So I begin to accept I was having replace the piston and liner of my new car at the cost of £40ish, so the hunt begins, guess what, I then find out that there is a problem getting hold of the GX21 pistons and liners and its probably going to take a least 2-4wks maybe longer, there’s a shortage. Now I’m very angry and upset as I’ve spent all that money and now have a buggy shaped DOORSTOP  and the worst thing is only thing I can do about it is buy a new engine. I was planning to do this but not for another couple of months. What am I meant to do Kyosho, HELP ME OUT PLEASE, I WAS GOOD ENOUGH TO SPEND MY HARD EARNED CASH ON ONE OF YOUR CARS CAN I PLEASE AT LEAST HAVE THE BACK UP. PEOPLE THINK I’M STUPID SPENDING ALL THE MONEY ON A RC CAR I DIDN’T!

Yours a very disappointed customer
Doby

Should have waited for that Hyper

 

[Çh®i§tiªñ]

While you have some VERY valid complaints, I just want to add some points for nitro engines accross the board.

1. The factory settings are purely a guideline. They will get you in the ballpark but its not uncommon to have to go away from these settings to get a good start.

2. Even the best of the best engines out there have problems from 1 tank, to 1 liter to 1 gallon. I once had an O.S. that was shot from the word 'go'. Fortunately O.S. is the ONLY company that carries such a comprehensive warranty and replaced my piston/sleeve for free. Took a month, but was free.

3. Manufacturer settings are based on where THEY are located, their altitude, barometric pressure, temperatures etc.. An engine made in Italy (high altitude) may run with completely different settings here in Buffalo, 600ft altitude, and require completely different settings.

Ultimately, tuning is purely in the hands of the owner and not something anyone else will be able to tell you. Again, only the mftr. setting are a baseline of where to get started. Everything else is on you.

My O.S. .21 RZV01B was set so rich when I first went to break it in that it literally would empty half a tank in 30 seconds (Woodie was there watching! lol). I had to lean in so much that I was almost scared. However, my running temps are at 210 farenheit and have never had a problem. The settings are completely out of the realm of what the mftr stated. Same with my Mugen MT .12. Wayyyyyyyy off. And my Picco .26 mills, forget about it! Those things are so far off from mftr. settings that I dont even use the manual!!!!

Now as far as your mill goes, they should more than like replace it. The fact that it failed so soon is a valid concern. If your temps were always low then more than likely it was a manufacturer defect. Most manufacturers are cool about it and will replace it. For a while, 1 out of every 2 Traxxas 2.5's sold was going bad right off the bat (I seen this at the LHS!!!). So good luck, hope they get you a new mill and in the meantime, just remember, not all settings are equal

 

[doby303uk]

mucho thx for the reply m8, you certainly got me thinking now
i do realise there is quite a lot to consider when running a nitro, weather conditions etc. and I'm still trying to grips with some of it, but i will say that me mill was also running quite rich all the time, visible smoke from me pipe at all times. anyways thanks for the info and hope i hear from Kyosho soon.

something else that we where thinking about, the exhaust breather pipe. take it the engine uses the pressure created from the exhaust to help push the fuel into the cylinder, so does a tuned exhaust just increase the pressure to push more fuel?

 

[Çh®i§tiªñ]

Pipes can increase/decrease the 'powerband' or range of throttle input. Yes they have an impact on performance and can require retuning when a different pipe is installed.

Some pipe give more low end punch while others will give you better high end/speed performance.

So much fun, so little time.

 

[robriguez]

I have the exact same car and have experienced the exact same problems. After 20-25 tanks of fuel it doesn't have anywhere near the same performance it did when it was new. I can turn the flywheel by hand very easily. Much much easier than I can the .12 and .15 motors I have. So, after a recent bashing session I thought that since I was going to buy a new engine anyway i would see if I can kill this one. I dont normally look at my needle settings but when I did this time they seemed way off. The HSN was way out and the LSN was protruding from the housing (normally it is slightly 'in') I readjusted everything and its right back to when it was brand new.

How did you come to determine that the piston and sleeve are done?

 

[doby303uk]

just checked me email nothing yet from ripmax or the shop i bought the car from

man i want to play with my buggy depressing

i may have a spare £120ish in the next couple of days, u guys think it be worth while investing in a new engine till i get the rbws7 2 + tuned pipe (couple months). which would you guys recommend, I see most of the top engine manufacturers produce cheaper engines but which would be best for my Inferno RB, OS, Picco? I'm looking for something punchy but with the top end to.

any1 know anything about thunder tiger engines? they any good