Planning on doing a top end rebuild on my 74 RD350. The bike has 30mm mikuni carbs and DG pipes. It still has the stock reeds so I'm planning on swapping those out for some TDR reeds. Do I need to rejet for the new reeds? I also put some cylinder head temp sensors on the bike. So I was wondering at what temps should I pull over and stop the bike. Past experience's tells me 400-425 degrees is the max temp before I have to start worrying about soft seizing. Hottest temp I got the RD350 to so far is about 350 degrees.
~420 has been the temp that I have always followed. Always try to do a plug chop read to make sure you dont put a hole in the piston as well. What senors are you currently running? Ive used the trail techs in the past.
You shouldn't need to rejet for the reeds. Hows the bike running at its current settings?
Write it down, Google doc or something and go for a long ride and then make the swap to see if there was a change. Doing this has saved me wonders of "what did I do I have in there?" And document the throttle position pull.
if you're running stock cages I agree, the jetting shouldn't really change.
Quote from: quocle603 on August 27, 2025, 07:59:07 AM~420 has been the temp that I have always followed. Always try to do a plug chop read to make sure you dont put a hole in the piston as well. What senors are you currently running? Ive used the trail techs in the past.
You shouldn't need to rejet for the reeds. Hows the bike running at its current settings?
Write it down, Google doc or something and go for a long ride and then make the swap to see if there was a change. Doing this has saved me wonders of "what did I do I have in there?" And document the throttle position pull.
I'm using a couple of trail techs. Figured I wouldn't need to change my jetting. In the past whenever I changed reeds it was always with modifications where I had to change jetting. The bike runs well so far. Its a little bit rich on the bottom end and pulls well until I hit about 80mph. On high speed runs I've been noticing that the bike starts to misfire and knock at around 7000rpm. I have the timing set up at 2.00mm BTDC so I'll try to bump it down to 1.8mm BTDC today and see if that fixes my issues.
The 1.8mm btdc will help with today's gas grade. Tons of mods to do on these bikes to "help" with performance but you sometimes take a loss. I would try to fit it best to your style of riding and preference.
make sure the float seat orifice is big enough and you're not starving the carbs.
My modified 400 seems to run about 280 degrees and up to 330 when opening it up.
I bumped the timing down to 1.8 yesterday and the bike runs a little cooler. I did end up finding out that my spark issues are from my condensers being bad, So I ended swapping those out for some extra condensers I had for my car.
On a side note would a bike with stock porting but bolt on modifications benefit from installing RZ350 intakes with the crossover tubes?
It might help with your mid range transition with those chambers, but i hear the DGs did not do much without modification. Do you currently have an issue with that right now??
Quote from: quocle603 on August 28, 2025, 03:22:39 PMIt might help with your mid range transition with those chambers, but i hear the DGs did not do much without modification. Do you currently have an issue with that right now??
No not really. I'm quite happy with my mid range right now. The powerband on the DG pipes doesn't feel peaky on the high end enough to justify a crossover intake. Assuming all the crossover intakes do is help with the low/mid range.
I would like to swap out my DG's for something else one day but I can't seem to find anything else.
Lomas makes pipes. specii but?
Quote from: quocle603 on August 28, 2025, 03:22:39 PMIt might help with your mid range transition with those chambers, but i hear the DGs did not do much without modification. Do you currently have an issue with that right now??
what does the modification involve?
I heard that JL stopped shipping pipes into the US. I would really like to try a pair of Spec ii pipes. Since I heard they work really well with stock porting. However, I don't know who to get in touch with to try to buy a pair. I remember seeing a website a few months ago but now it's gone.
i hope not. i have a set waiting to come in.
Quote from: Scuffed98 on August 28, 2025, 05:22:30 PMI heard that JL stopped shipping pipes into the US. I would really like to try a pair of Spec ii pipes. Since I heard they work really well with stock porting. However, I don't know who to get in touch with to try to buy a pair. I remember seeing a website a few months ago but now it's gone.
I would probably just keep the stock intakes instead of the banshee ones with crossover. Do what you will but your bike is pretty much stock with dg and 30mm carbs. How are the 30mm carbs? I assume they are VM
What are you looking to achieve? If you want high rpm hitting pipes, then try to find lomas and spec II. I have an extra set of spec II that I was able to pick up for under 300 bucks locally.
Quote from: RDnuTZ on August 28, 2025, 05:17:08 PMQuote from: quocle603 on August 28, 2025, 03:22:39 PMIt might help with your mid range transition with those chambers, but i hear the DGs did not do much without modification. Do you currently have an issue with that right now??
what does the modification involve?
I had the pdf but somehow I lost the data somewhere... https://www.2strokeworld.net/forum/index.php?topic=726.0
Wicked is selling pipes for the RDs; Roger just posted about it on FB
Quote from: quocle603 on August 28, 2025, 06:13:18 PMQuote from: Scuffed98 on August 28, 2025, 05:22:30 PMI heard that JL stopped shipping pipes into the US. I would really like to try a pair of Spec ii pipes. Since I heard they work really well with stock porting. However, I don't know who to get in touch with to try to buy a pair. I remember seeing a website a few months ago but now it's gone.
I would probably just keep the stock intakes instead of the banshee ones with crossover. Do what you will but your bike is pretty much stock with dg and 30mm carbs. How are the 30mm carbs? I assume they are VM
What are you looking to achieve? If you want high rpm hitting pipes, then try to find lomas and spec II. I have an extra set of spec II that I was able to pick up for under 300 bucks locally.
Whats the powerband rev range on JL's and spec ii's? As cool as would be to have my bike be a 10,000+ screamer I know for a fact that with the stock rotor and points my crank or ignition won't like that. I'm going to upgrade to a dyna ignition whenever I get around to doing the top end. My main goals for the bike is pretty much keep it decently streetable but also to have enough power on tap on the freeway to hit the 120mph max on my speedo.
Be careful with using head temps. They aren't that useful, I have seen Yamaha's run 580F CHT and be fine. It's a target temp based on ambient, and in a flat out run you will always be hotter than putting around.
For racing we always do ambient temp less baseline temp. So if it's 90F out and baseline is 60F, you take the 30F difference and add it to your target Temp. Which makes your 450F a 480F CHT temp.
CHT is a lot more useful in constant state engines like on airplanes. EGT on a motorcycle works great. I have had it on my 350 for a decade.
As for JL's. I spoke with Jim about two months ago. No mention of tariff/shipping stuff at the time, but he did say he builds all his street pipes for the street. As in, they are definitely brought into check somewhat. He didn't want to go into specifics...
The DG mod is a great mod, but its a fair amount of messing around. You can make the pipes significantly lighter too. It was worthwhile on my build.
my jl pipes (for the t500) are on the way, just got the ups notification last night. so, they are shipping. On my rds, I have both spec-iis and Lomas on 2 different bikes, anything over 92-9500 is pure over-rev as that's about where they sign off. both are ported and will spin PAST 10, but the pipes sign off a bit earlier. my rev limiter is set to 10.2 in case of overrev (by a heathy margin). 11k is sort of the death zone and there's no reason to spin a 350 near that high
Quote from: quocle603 on August 28, 2025, 06:36:02 PMQuote from: RDnuTZ on August 28, 2025, 05:17:08 PMQuote from: quocle603 on August 28, 2025, 03:22:39 PMIt might help with your mid range transition with those chambers, but i hear the DGs did not do much without modification. Do you currently have an issue with that right now??
what does the modification involve?
I had the pdf but somehow I lost the data somewhere... https://www.2strokeworld.net/forum/index.php?topic=726.0
thanks :thumbs:
Quote from: m in sc on August 29, 2025, 12:33:04 PMmy jl pipes (for the t500) are on the way, just got the ups notification last night. so, they are shipping. On my rds, I have both spec-iis and Lomas on 2 different bikes, anything over 92-9500 is pure over-rev as that's about where they sign off. both are ported and will spin PAST 10, but the pipes sign off a bit earlier. my rev limiter is set to 10.2 in case of overrev (by a heathy margin). 11k is sort of the death zone and there's no reason to spin a 350 near that high
On your RD's with the spec II's and Loma's did you have to do a lot of porting on the cylinders?
both were ported pretty extensively but for power. i have another one with FPPs, also considered peaky pipes, with dead stock porting & zero headwork. THIS is the bike where the ignition really shines. theres a fairly recent video i took on it showing its useability in the low to mid range in the 'haus of projects' on my 72 r5. yes, its a full rd motor in there. even running stock carbs.
last page:
https://www.2strokeworld.net/forum/index.php?topic=2693.60
:twocents:
For those of you running CHT gauges what kind of temp variance are y'all seeing between your cylinders? I've been seeing an average of 10°-20° CHT difference between my left and right cylinders and spikes of 30°-40° during wot.
Mine would be 30 degrees different at times. After fresh pistons they stay about 15 with each other. Maybe check carb sync and timing if you have points or Dyna ignition.
I've been trying to re-jet the bike since I did the top end. I did check the carb sync by looking at slide movement with a mirror and they are synced up and I double checked my timing to verify that it is firing a 2mm btdc. I've had to bump the pilot jet up from a 27.5 to a 35 to get it to idle well. Right now, I'm stumped on my main. Once I get past 7000rpm above 4th gear the power becomes flat. The revs keep climbing slightly and then they go back down. So I'm not sure if it's an issue with my main jet or if my clutch is worn out.
is it in 4th 5th and 6th? but 1,2 3 ok? might be starving the bowl
Quote from: m in sc on October 22, 2025, 05:54:22 PMis it in 4th 5th and 6th? but 1,2 3 ok? might be starving the bowl
1,2,3 is fine, 4th starts hesitating a little once I hit 8k and at 5th and 6th power curves completely flattens out at 7k. If I'm cruising below 7000 in 5th or 6th the bike acts fine, it only really occurs during hard acceleration in my top gears.
If it is starving the bowl, what would I need to do to remedy it?
could be the petcock flow, tank vent, etc. what size mains are in there?
Quote from: m in sc on October 22, 2025, 06:51:08 PMcould be the petcock flow, tank vent, etc. what size mains are in there?
220 mains right now
regular petcock and everything should flow fine. check for restrictions. my advice is: clamp off 1 line, take the other off, and put a long line on it. put line in a gallon jug, turn fuel on. watch the flow for about 2 mins. if it reduces over that 2 mins, you have a restriction somewhere .
Just performed that test and there was no fuel flow reduction over a 2 minute period. The only indication of flow reduction I got when the tank was near empty on reserve. The line that goes to the RH carb started flowing droplets while the line for the LH carb was still flowing albeit weakly. Although I'm not sure if this is any indication of my issues since I try to keep the tank filled above half. Interestingly when I testing the petcock one port at a time if I pulled off the plug off one of the fuel port with a hose on the other the open fuel port wouldn't spill any gas unless I hooked a fuel line back onto it.
you need to pinch one line off or cap it completely or it will pull air up through one. this can and will give incorrect results if you dont. trust me on this. :twocents:
almost sounds like a vapor lock