Race Port Engine Not Pulling RPM

J

JB.SRX700

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Hey guys new to the forum, I looked for a topic on this already and wasn’t able to find one. Here’s what’s going on, this year I just got my 02 srx done by Iantomasi. My invoice states “full race port”. Has 14:1 ratio, 36mm carbs, heads shaved, case and cylinder porting, Vforce reeds with spacer. I’m running aaen pipes was very happy with them last year stock sled was running 118 at 8400 on gun every time I was at a radar run. Sled is still at same set up as last year with 23/40 gears, green spring 51/43 helix wrapped at 70, www primary 8bu-00 at 54g. Got engine back and I can’t pull rpm It will only rev 8000-8100. Powervalves were set, I am very rich as I have 160 mains with needle at #4. I am going to try 157.5 just wasn’t sure if any could help me out as maybe there is something else I need to do??
 

More info required:
_Where are you located?
-altitude and temperature you are trying to jet for?
-What RPM did Iantomasi specify that the engine should run at?
-What 36mm carbs are you using?
The porting may not be compatible with the Aaen pipes.
I would concentrate initially on the jetting of the 36mm carbs before I touched the clutching as a full race ported engine should want to exceed the rpm the engine previously pulled.
I have used Aaen pipes on a 2002 SRX in the past and I found them very particular at the RPM they ran at .
When rejetting the carbs be very conservative and ensure you are using good fuel as you do full throttle runs and read plugs and piston wash.
 
sideshowBob said:
More info required:
_Where are you located?
-altitude and temperature you are trying to jet for?
-What RPM did Iantomasi specify that the engine should run at?
-What 36mm carbs are you using?
The porting may not be compatible with the Aaen pipes.
I would concentrate initially on the jetting of the 36mm carbs before I touched the clutching as a full race ported engine should want to exceed the rpm the engine previously pulled.
I have used Aaen pipes on a 2002 SRX in the past and I found them very particular at the RPM they ran at .
When rejetting the carbs be very conservative and ensure you are using good fuel as you do full throttle runs and read plugs and piston wash.
Click to expand...
Thanks for the reply Bob
I’m located in Ontario,
Trying to jet for -5 to -10 as our winter have been mild
As for altitude I’m roughly 195 metres
I was never given a rpm range to run the engine so I have no answer for that, my carbs are stock srx carbs that tamosi bored out to 36mm. I am at 160 which I know is fat I needed somewhere to start and wanted to be safe. I am dropping down to 155s. I was running 94 octane and used vp booster to get to 100 octane, (tamosi cut heads for 100 octane) today I have bought gulf 112 I will be draining tank and putting the 112 by its self as I was told it’s realisticly 105.
 
sideshowBob said:
More info required:
_Where are you located?
-altitude and temperature you are trying to jet for?
-What RPM did Iantomasi specify that the engine should run at?
-What 36mm carbs are you using?
The porting may not be compatible with the Aaen pipes.
I would concentrate initially on the jetting of the 36mm carbs before I touched the clutching as a full race ported engine should want to exceed the rpm the engine previously pulled.
I have used Aaen pipes on a 2002 SRX in the past and I found them very particular at the RPM they ran at .
When rejetting the carbs be very conservative and ensure you are using good fuel as you do full throttle runs and read plugs and piston wash.
Click to expand...
I have tried multiple times to call Aaens preformance and email them trying to get info on their pipes to see what rpm they like I have read on here they built them to run 8300-8500 to be in range for srx cdi. I have heard they make race pipes and trail pipes but on their website I can only find 1 part number for the srx
 
When I ran the Aaen pipes on my ported 2002 SRX I found stock RPM or maybe max 8800[with some timing advance]was where they seemed to perform the best. As you stated the ECU on the SRX was designed to run @ 8500 and starts to pull timing after that.
With a full race ported engine you may be into an incompatibility with the ECU and the pipes as the porting may be optimum at a much higher rpm then stock.
On the 02 SRX you can use the ECU off of a 2002 Viper maybe for only drag racing as it will work but it will render the DCS system inoperative. The Viper ECU has much more timing so mid range jetting, fuel, and heat become very important for engine survival. The Aaen pipes on a Viper were run at @ 9000 rpm but I believe the Viper pipes were slightly shorter to get that RPM and due to different cylinders and manifolds they are not interchangeable.
I would contact the company that ported the engine for recommendations on RPM, PIpes [stock might be better], and jetting.
With your present setup cautiously move to smaller main jets and target 8400 RPM and see how things work out. I would think 152.5 jets are about as max lean as this setup should be and that may be too lean.
 
sideshowBob said:
When I ran the Aaen pipes on my ported 2002 SRX I found stock RPM or maybe max 8800[with some timing advance]was where they seemed to perform the best. As you stated the ECU on the SRX was designed to run @ 8500 and starts to pull timing after that.
With a full race ported engine you may be into an incompatibility with the ECU and the pipes as the porting may be optimum at a much higher rpm then stock.
On the 02 SRX you can use the ECU off of a 2002 Viper maybe for only drag racing as it will work but it will render the DCS system inoperative. The Viper ECU has much more timing so mid range jetting, fuel, and heat become very important for engine survival. The Aaen pipes on a Viper were run at @ 9000 rpm but I believe the Viper pipes were slightly shorter to get that RPM and due to different cylinders and manifolds they are not interchangeable.
I would contact the company that ported the engine for recommendations on RPM, PIpes [stock might be better], and jetting.
With your present setup cautiously move to smaller main jets and target 8400 RPM and see how things work out. I would think 152.5 jets are about as max lean as this setup should be and that may be too lean.
Click to expand...
Okay I am going to cut back on my fuel until I have nice piston wash and plug colour. Put the good race fuel in and see what happens from there. Hopefully I can a gain in some rpm, my buddy has exact sled as me with same clutching gearing ext. except 01 and same porting stock pipes. His sled worked good until he put the same carbs and jetting in that I am running he now can’t pull rpm either so I’m believing we are into a carberator issue (fingers crossed). I will be testing today or tomorrow and will tell you with the out comes. Also I do have a viper cdi and always planned to jet high to compensate then hotter timing curve if that will work?, have you ever heard of moving the pick up a bit to bump timing up for stock srx cdi??
 
I used a 2 degree flywheel key on my 2002 SRX and installed it to advance the timing.
I did a lot of work to my 2002 SRX to gain performance but it never was as quick and fast as our Ported and Bender piped ect 700 SX redhead was...close but not quite there.
 
sideshowBob said:
I used a 2 degree flywheel key on my 2002 SRX and installed it to advance the timing.
I did a lot of work to my 2002 SRX to gain performance but it never was as quick and fast as our Ported and Bender piped ect 700 SX redhead was...close but not quite there.
Click to expand...
So here’s an update. I have put the good fuel in, I reset powervalves to be sure, still not pulling rpm ranging anywhere from 7600-8000. I tried stock heads in case the new ones were not working. I have played with secondary clutching, I’m down to 155 mains starting to have pretty nice plug colour I checked wash but only have 50miles on sled so there isn’t a lot of colour going on the pistons yet. I am going to try stock pipes just as one last thing before I am unfortunately going to have to send this damn thing to someone to have it put on a dyno and get tuned. Have a lot of money into this engine now and just want it to work.
 
JB.SRX700 said:
So here’s an update. I have put the good fuel in, I reset powervalves to be sure, still not pulling rpm ranging anywhere from 7600-8000. I tried stock heads in case the new ones were not working. I have played with secondary clutching, I’m down to 155 mains starting to have pretty nice plug colour I checked wash but only have 50miles on sled so there isn’t a lot of colour going on the pistons yet. I am going to try stock pipes just as one last thing before I am unfortunately going to have to send this damn thing to someone to have it put on a dyno and get tuned. Have a lot of money into this engine now and just want it to work.
Click to expand...
Have you revved it out on a stand and observed the pulley operation for the servo motor?
 
Another thing to check is the TPS setting. Since you have increased the carb size from 33mm to 36mm you are now pulling the slides a lot higher which also rotates the TPS and that will alter the TPS voltage to the ECU. Try adjusting and setting the TPS to the stock setting and see if that helps. The procedure is in the maintenance manual and also should be information on TPS issues if you do a search.
If you have a stock carb rack you could try installing the stock carbs and see if the bored carbs are causing an issue.
 
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Did u know what type of porting they did ..exhaust and intake duration .. did u try the stock clutch to start
 
So guys got out for some testing this year ran out of season last year. Came to a bit of conclusion that I the pipes I was using weren’t compatible with the race port engine. Now I have got jaws to make me a set of race pipes 9600-9800. I have viper box I’ll be running to have timing at that rpm. Ran sled today it is better. How ever now I am looking for a good baseline for clutching/ gearing for 1/4 mile. I am needing to come up 1300 rpm.
Here is current set up. 23/40 gearing, www primary with 8dn-00 weights at 54g, green secondary with 51/43 helix wrapped at 70. degree. Right now from a dig I hit 7900rpm and at 1/4 I am about 8200rpm. I have a 45/39 helix I am hoping to use. And was either going to go with 23/38 gearing or 24/38 My first move was going to be remove all the rivets from my weights and see what I come up with for rpm. What are your thoughts?
 
Yes, you need lighter weights to get your rpm way up.
Yamaha only used those weights on the 1998 model, then quit them as they were known for breaking.
What other weights do you have?
I always liked the 8DN-20.
 
74Nitro said:
Yes, you need lighter weights to get your rpm way up.
Yamaha only used those weights on the 1998 model, then quit them as they were known for breaking.
What other weights do you have?
I always liked the 8DN-20.
Click to expand...
Today I got my hands on a borrow set of heel clickers possibly from a 4 stroke long story short I took all the weight out of them and they weighed out at 52g. My 8bu’s are actually 56g I checked today, so I installed the heel clickers at 52g with my www primary, I swapped my helix out to 45/39 green spring wrapped at 70. With the stock srx cdi on it I went for test drive. From a stop I pin it and it goes to 8900 and it hits about 9100 when fully shifted out. Since I was now revving I plugged in viper box for timing and lots of plug checking I now stab throttle from a stop and it goes to 9500 and after fully shifted it lays about 9700-9800 rpm right where I need to be. I was on about 1 - 2” of snow marked off 1/4 mile. Ran 113. Fairly happy with results considering I was not on a nice plowed track. I’m going to play with gearing now. Once I have the desired gear set I am going to put in my 8DN-20s which are also at 52g and see what happens there, the heel clickers and 8DN-20 have a very similar profile on them how ever the 20s do seem to have a slight bit less angle out at the tip. I’m not sure what the rivets on the weights are as they are stock but does have 2 rivets in them. I’m thinking I will be wanting loose all top weight and add what I need to make up the 52g in the heel. We are going in the right direction now and I am very happy with finally having some decent results. Everyone on here has been a great help and I am very appreciative of it you guys rock!!!!!
 
sideshowBob said:
Great! Good to see things are going in the right direction.
Click to expand...
Thanks for all the information every little bit helped! Do you happen to know a good gearing for 1/4 mile? Have read stock isn’t bad, also heard maybe 23/37 is good?, I like the idea of 24/40 as it is a similar ratio to stock but bigger gears may make for less resistance!
 
Stock will be good for 1/4 mile. Are you looking for et or mph?
When I grass dragged these I ran 20/40 for 500ft.
 
Okay I’ll give it a try, looking for mph for the most part. I read on here the red primary spring seems to be a common spring to run for a hopped up engine. I’m assuming that’s an all red spring from dalton?, I seen a post from mrviper saying if your running your weights empty you have the wrong set up mine are currently empty so I’m thinking I need a stiffer primary spring and then add weight for desired rpm
 
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