×
Pictures Posting Not Working (12 Jun 2023)
Picture uploads is again unavailable. We are working on the problem. Thanks for your patience.
Makotosun
Leak down test. Initial set-up, problems, fixes and results.
- Andy L
- Topic Author
- Offline
- Site Supporter
- Posts: 108
- Likes received: 98
Replied by Andy L on topic Leak down test. Initial set-up, problems, fixes and results.
......Thanks. That's what I thought, but wasn't sure if some sort of adhesive was implied.
Okey dokey, that is good news because it implies that as the bike get used the heat generated over time will in fact make the carb rubber to reed valve box seal better and better.
Okey dokey, that is good news because it implies that as the bike get used the heat generated over time will in fact make the carb rubber to reed valve box seal better and better.
24 Jun 2021 03:47
#11
Please Log in or Create an account to join the conversation.
- RT360Fan
- Offline
- Site Supporter
- Posts: 471
- Likes received: 191
Replied by RT360Fan on topic Leak down test. Initial set-up, problems, fixes and results.
Here's the thing. . .
These bikes are 40-50 years old. NOS gaskets may have been sitting on the shelf for as long. Things tend to warp, degrade and change over many years. Furthermore, Yamaha has been known to change materials and specs over time. Just saying that some sort of adhesive *may* be necessary to get a good seal, even with an OEM gasket. Yamabond 5 is a good one. Personally I use Hylomar Blue on *difficult* intake gaskets. If you end up using a sealant do so sparingly. If it's noticeably oozing out after tightening you've used waaay to much (IMHO).
Good luck, hopefully the new gasket will work fine.
These bikes are 40-50 years old. NOS gaskets may have been sitting on the shelf for as long. Things tend to warp, degrade and change over many years. Furthermore, Yamaha has been known to change materials and specs over time. Just saying that some sort of adhesive *may* be necessary to get a good seal, even with an OEM gasket. Yamabond 5 is a good one. Personally I use Hylomar Blue on *difficult* intake gaskets. If you end up using a sealant do so sparingly. If it's noticeably oozing out after tightening you've used waaay to much (IMHO).
Good luck, hopefully the new gasket will work fine.
Please Log in or Create an account to join the conversation.
- MarkT
- Offline
- Site Supporter
- Posts: 13518
- Likes received: 9369
Replied by MarkT on topic Leak down test. Initial set-up, problems, fixes and results.
They are talking about the boot "welded" to an aluminum plate... basically the rubber is formed over the plate. They are NOT talking about the boot plate being "welded" to the reed cage. They are separate parts and always have been.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
The following user(s) Liked this Post: RT360Fan, Andy L
24 Jun 2021 16:17
#13
Please Log in or Create an account to join the conversation.
- RT360Fan
- Offline
- Site Supporter
- Posts: 471
- Likes received: 191
Replied by RT360Fan on topic Leak down test. Initial set-up, problems, fixes and results.
Ahhh yeah. Re-reading the post showing the pic of the Yama manual I get it now. Thanks Mark.
Please Log in or Create an account to join the conversation.
- Andy L
- Topic Author
- Offline
- Site Supporter
- Posts: 108
- Likes received: 98
Replied by Andy L on topic Leak down test. Initial set-up, problems, fixes and results.
Yep, the Penny's dropped for me too. Thanks for the explanation Mark.
24 Jun 2021 23:24
#15
Please Log in or Create an account to join the conversation.
- Andy L
- Topic Author
- Offline
- Site Supporter
- Posts: 108
- Likes received: 98
Replied by Andy L on topic Leak down test. Initial set-up, problems, fixes and results.
Well the NOS carb gasket arrived and although from the on-line pictures it looked thicker than my existing gasket there wasn't a lot in it. Checked thickness and both were a shade under 0.7mm. Anyway I fitted it in place and repeated the leak down pressure test from 5psi(g) and no appreciable change in test result. It still leaks from the gasket joint (5 to 2.5psi(g) over 10mins). I didn't really want to go down the next route because it is messy and hassle if I need to take the reed cage/carb boot unit off the bike again, but I have smeared silicone sealant over both sides of the gasket (used sparingly as RT360Fan advised) and sandwiched it all back up with the bolts lightly done up. Therefore now another 24Hr curing period, so that's all for the moment. Andy.
26 Jun 2021 08:02
#16
Please Log in or Create an account to join the conversation.
- MarkT
- Offline
- Site Supporter
- Posts: 13518
- Likes received: 9369
Replied by MarkT on topic Leak down test. Initial set-up, problems, fixes and results.
I'm still going to warn you that I'm 99% sure that sealer will fail eventually. Silicone sealants like Pro Seal are at best "oil resistant" and when exposed to modern gasoline will soften and disintegrate with use over time.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
The following user(s) Liked this Post: Jack
26 Jun 2021 08:25
#17
Please Log in or Create an account to join the conversation.
- Andy L
- Topic Author
- Offline
- Site Supporter
- Posts: 108
- Likes received: 98
Replied by Andy L on topic Leak down test. Initial set-up, problems, fixes and results.
Bad news.......then finally good !!
This image is hidden for guests.
. Apologies for the extended delay in submitting this post. The delay was caused by my decision to heed the advice I'd received regarding the silicone sealant I'd used on the gasket between the reed cage and cylinder (jug) inlet metal face. The bad news then is the additional work it gave me. I discarded the gasket with silicone sealant on it, cleaned all the faces free of silicone
This image is hidden for guests.
and instead lightly smeared my original gasket with Hylomar Blue which is definitely compatible with gasoline (it says) and tightened everything back up to 8Nm. The good news is that using my brake bleeder as a pressure pump (see pic 1) I pumped everything up to the test pressure of 5psi(g) see pic 2 and it passed easily, maintaining pressure for over 15mins after which I ‘relaxed’ it back down to 0 psi(g). More good news was that I flipped the brake bleeder pump over to suction (pic 3) and vacuumed the crank plenum down to -5 psi(g) as shown in pic 4 and again it held for well over 15mins till I relaxed it back to 0 psi(g). That concludes this leak down test and I can now continue getting the rest of the build on track. Thanks for all the help forum members have offered and it's been a great learning curve for me as a leak down test 'newbie'. Andy.
This image is hidden for guests.
Please log in or register to see it.
This image is hidden for guests.
Please log in or register to see it.
The following user(s) Liked this Post: Pete-RT1
This message has attachments images.
Please log in or register to see it.
Please Log in or Create an account to join the conversation.
- MarkT
- Offline
- Site Supporter
- Posts: 13518
- Likes received: 9369
Replied by MarkT on topic Leak down test. Initial set-up, problems, fixes and results.
Congratulations! Nice job!
This image is hidden for guests.
(And yes, Hylomar blue should work great)
This image is hidden for guests.
Please log in or register to see it.
(And yes, Hylomar blue should work great)
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
29 Jun 2021 05:23
#19
Please Log in or Create an account to join the conversation.
Moderators: yamadmin, Makotosun, DEET, Vinnie, James Hart