HPI RS4 3

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FirsthandSnow

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hey, I posted a week or so ago about finding a relatives RS4 from 2002-4. I've found that everything is essentially the same on the newer models as on the old, which is helpful. However I'm trying to mount a G3.0 engine, using a 21mm brace, but I find that the nut on the carb is wedged against the brake pads, and as its a rotary carb and requires space to move in and out, the engine wouldn't be able to open up. Any ideas? :]
Also I'm using a 47 tooth spur (HPI-76867) and a 19t clutch bell, which don't seem to mesh well at all...
Anybody with more knowledge than me, please help aha
Thanks Crew
 
Any pics you could post would be very helpful in this case. Please post a few from different angles esp from where the interference lies as well as from the mounting locations and we'll try out beat to help you out.

Also, just a quick couple thoughts... According to the manual, are the gears you are using what is called for when it was built? If not, how far off are they? Is there a motor mount that came stock that you aren't using or are unable to use with your motor?

Doing a quick search, I am also wondering if there are different mounts between a pull start and non which use different mounts also? Again, your manual would likely have that info.
 
Last edited:
Sorry to keep adding here but I keep finding new info. If what I have read is accurate, it seems that this car uses a 2 speed spur/pinion set up. It is based on 48 pitch gears HOWEVER... It seems that these gears are made to mesh with each other individually. In other words, in order to mesh properly, hpi made these gears so that they would actually be a 49 or 50 (for example) pitch on one pair of gears while the other pair may be an actual 48 pitch gear.
Is the motor you are using actually from or for this particular car? An oversight from the beginning on my part but I am wondering if you are using a rotary carb and the car calls for a slide carb. I am not into on road but I am familiar with the purposes of the slide carb vs rotary. As I have understood, the slide style is what you want to use in an on road due to its performance characteristics. The physical differences in these carbs could certainly account for the incompatibility in mounting.
 
Wow! Thanks for all the help and thoughts :] Firstly, this is a really old RS4, it was only single speed, I've replaced a shredded spur gear with the exact same spur, but I'm using a different engine, a G3.0. The RS4 comes with a T3.0, which in certain is the same engine, but just doesn't need a brace to mount it. I was also thinking about the pullstart, I'm thinking it's making the engine sit funny, I'll take it off and put on a spare rotostart :] Although I've always preferred a pullstart :[ I'll take some pictures this evening and post them, thanks again.

P.S. If the clutch bell won't mesh properly, I'll just install the 2-Speed tranny and hope for the best aha
 
Is it possible that you have a single funky pitch gear trying to mesh with a normal gear?
Don't feel too badly here... I am slowly working on an rc10gt... The spur gear is so low (missing trans spacers I think) that it actually are a hole in the rear arm mount! Talk about a weird mesh!!!
The guy I got it from races it like this!. Entire brake system missing from car and a lot of misc weird stuff... Smh!!!
 
Hi guys, sorry for the late reply, been a bit busy the last few day :) As soon as I got a chance I sat down and tried to mesh the gears, I got them to mesh just about right, for the time being, but I've now hit another 2 problems, with the transmitter and receiver. I have the TF-20E transmitter and RF30 receiver for this car, salvaged from another. When I hold the brake on, the servo moves to the brake position, for around 2 seconds, then moves to the accelerate position and then back to brake position. the longer I hold the brake fully, the longer it will cycle through doing that :eek: Also I have found that the transmitter just stops transmitting anything and servos lock up, and may or may not reconnect to the transmitter. I tried to bind the Tx and Rx, following the instructions, and nothing happens, the red light on the Tx keeps flashing on and off, however, I found that will in the bind mode(?) the Tx never loses connectivity with the Rx and the servo doesn't have a fit. Strange... Problem is i can't keep putting the car and Tx in bind mode every time I want to use it aha
I will probably need new electronics I am guessing :]
 
Try a new battery first. A weak RX battery can cause brownouts that sound like your problem.
 
You may also be experiencing some high frequency noise created by metal to metal... It's a known issue but I am no expert about it. I would suggest that you may move your RX in the car and be 100% sure that your wires are as far away from the motor or any other metal to metal that's moving. Its gotta be worth a shot over buying new gear. Let me know if it helped.
 

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