I just got me a slightly used RB WS7T, apparently it only had half a gallon through it. I used it for the first time in race replacing the GO 21 5 port I had in there previously. The engine is in Hyper ST Pro running a 14T CB and a 2047 pipe and header combo. I run Byrons 25% Gen 2.
I do have a few questions though. Perhaps you can help me on this one.
1. The engins hs no mechanical pinch at all, but tons of compression, is this normal on RB's after 1/2 a gallon?
2. Engine ran great all day during the qualifiers, but when it came to the race it started acting strangely. It would have no drive out the corners and then all of a sudden, a literal explosion of power, needless to say this caused a few off track excursions. What would cause this? For the first 4 or 5 laps, it was great and then started doing this.
3. My needles were are at factory settings, which to me seems to be way too rich with Byron's Gen 2, could this have caused my issues in the race. I never touched the needles from qualifying to the race at all.
4. Also, what pipe would be great for this engine? The 2047 seems decent, but on my mates Ninja B01A, he tried it and then the **** and found the **** to be a much better suited pipe, it had a lot more low down and still great top end. What would you guys recommend. I race on a variety of tracks from hard and bumpy to smooth and dusty, also very technical with some good triples and doubles.
Thanks for any advice.
Cheers
Posts: 30 | From: Surrey, UK | Registered: Dec 2007
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It sounds like the motor got hot and developed a low end bog from running too lean on the lsn.
It prob didnt get hot enough in the 5min qualifying rounds. I've had this happen and its almost impossible to drive in a race.
You need to tune the HSN right then set the LSN correctly and it should be all good. If the engine has loads of compression I wouldnt worry about pinch.
Posts: 49 | From: UK | Registered: Sep 2007
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It was actually tuned by one of the guys who run the same engines from the LHS just before the heats. I know my pit mate richened up the bottom end a little before Heat 3 to try and calm down the mad bottom end. These settings weren't touched at all again. The weather was quite warm yesterday, approaching 24 C. We never temped the engine at all yesterday.
Would it still run lean on the LSN set to factory?
Also meant to add that in the qualifiers including the few minutes before and the slow down lap, I managed to do 12 laps in total at one stage. I didn't even manage half that before the issues in the a-main.
[ 23. June 2008, 15:33: Message edited by: squeeguk ]
Posts: 30 | From: Surrey, UK | Registered: Dec 2007
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did you check your clutch.. one of your springs may have broken or your clutch was slipping so much that it heating up and starting biting to hard cause a bog...
Posts: 207 | From: usa | Registered: Apr 2006
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Please note that the factory settings are just points to start the engine and let it roll. I would say that the factory settings are way too rich on the LSN when using racing fuel. Also on the HSN but not that much. When the engine ran great throughout the qualifiers then I also would check the clutch. As you said, it started to do so after 4 or 5 laps that also were achieved in the qualifiers which let me think that it's not related to the engine's settings. Maybe a truggy with a 14T bell in combination with the WS7T overheats the clutch, thous the clutch couldn't take it and got weak in your main run. As said, I also would check the clutch and maybe use a 13T or even just a 12T bell or maybe the pipe provides not enough bottom end.
[ 26. June 2008, 12:35: Message edited by: Stefan ]
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Hi Squeeg, I'm guessing your running the Hyper ST with the WS7T? I run both S7 and C6 in my ST and have found that a 13 tooth bell is the best bet. You do loose a little top end, but the response on the bottom end is much better, and clutch life and performance is maintained.
Posts: 26 | From: Southampton, UK | Registered: Nov 2007
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Thanks guys. The clutch was brand new when I started the day and apart from a little burring looks fine, the springs are all intact too. How long do you guys find your clutches last with these engines?
Perhaps I need to change to a smaller CB?
I have another race on this weekend, so I'm going to spend a lot of time during practise checking it all out properly. I wil run a full tank through and check the temps at the end of the run.
Posts: 30 | From: Surrey, UK | Registered: Dec 2007
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so it also can't be related to the clutch then. For the CB, patriotboy runs a 13T on his ST as said. This will give more "activity" to the driving. But that's not the problem you are describing here if the clutch looks fine. Then I have one more thing that would come up exactly like Backroomsam is saying, a broken pressure line (lid's o-ring, nipples) maybe. After 4-5 laps the tank is filled lower and with a broken pressure line the engine reacts the more difficult the lower the tank is filled and it runs hotter, too.
My CS last about 15L when carbon and about 5+L when alu. I run the RT Speed 2.5 (not extended) with stock Kyosho 13T CB in the buggy.
[ 27. June 2008, 11:40: Message edited by: Stefan ]
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The Hyper ST tank lid is notorious for failing and not sealing properly. Try screwing in the cross-head screw under the lid by a turn or two to compress the o-ring a little more, and then blow down the return line to check for leaks.
I had this exact same problem with an S7, and traced that to the tank in the end.
Posts: 26 | From: Southampton, UK | Registered: Nov 2007
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OK, guys, had another race today with the same issues.
I had to richen up the bottom end and then continue the race, then it was fine.
Problem is when it came to starting the engine again, it was so rich, I couldn;t even get it warmed up at all. It wouldn't rev out at all.
I changed the ruel tank and used 2 different pipes, I even double checked the tank seals, replaced all the fuel lines and nothing. Always seems to manifest itself after about 3 to 4 laps. It's really irritating, it becomes like a switch every time, really hard to drive like that. I did a 39.1 on the only decent lap I had before the trouble started and then my times dropped off by about 8 seconds.
I had another 2 pros who run the same engine have a look at it today and they both had tries at tuning it, same story. I even changed to an old 9863 (I think) pipe that one of them had around.
Any other advice? I will be investing in a RB 2045 pipe for it. Hopefully that will make some difference.
This is driving me nuts.
[ 29. June 2008, 21:47: Message edited by: squeeguk ]
Posts: 30 | From: Surrey, UK | Registered: Dec 2007
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maybe a leaking front bearing drawing air into the engine when it gets warmed up.
the engine will run ok upto around 3-4 minutes then it will loose all its bottom end,no matter what you do to the needles it wont go away of thats the cause.
dave
Posts: 5 | From: uk | Registered: Jun 2008
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I have no idea, I will need to check that. But with the engine out of the car and holding the flywheel, I can actually bounce the engine on compression, it won't go past the compression, so I should imagine it has decent compression when hot.
I have it all stripped out of the car now, so won't be able to tell. I am going to get the front bearing changed as a matter of course.
I so want to like this engine and I want it to be as great as everyone says.
[ 30. June 2008, 16:06: Message edited by: squeeguk ]
Posts: 30 | From: Surrey, UK | Registered: Dec 2007
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I just took the carb off the engine and had a look at the front bearing too. Front bearing is clean, not s spot of oil or anything on it. Does that mean it's ok? As for the o-ring in the bottom of the carb, it's all 100%.
My mate wants to go and buy one of these now, but is worried after seeing the issues I have been having.
Posts: 30 | From: Surrey, UK | Registered: Dec 2007
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Hard to tell you what the issue could be, I do not think that it is the front-bearing especially when it is still clean but more a tuning issue if I read through the topic. Before making all kinds of changes, try another type of fuel although I think byron should be good. You could also check the car, maybe something starts binding when it becomes warm, this is something I encountered too. Hope this helps.
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