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Messages - 400 Cafe Racer
1
« on: March 28, 2025, 07:07:50 PM »
Rust away.
After starting, Don't stop the engine until the exhaust is really hot, this will help to get rid of condensation and rust formation in the collector box. 
2
« on: March 26, 2025, 09:05:31 PM »
Hi Guys,
I had a Kit from DS to overhaul the 50 year old petrol tap and also ordered their "O" rings for the seal between the tap body and the rotating handle. It was suggested that 2 would be necessary as 1 would not always seal !!
After carefully cleaning all parts before rebuilding I measured:-
1. the outer seal face of the rotating handle - then the inner seal face of the tap body.
2. the O/D and I/D and cross section of the OLD seal
3. the O/D and I/D and cross section of the NEW seal
Because the sealing faces are the inner and outer circumferences the cross section or thickness is vital to prevent leakage.
Measuring the DS seals they are undersize in thickness to make a seal and actually leave a clearance gap for petrol to leak through, so putting 2 in as was suggested is an incorrect solution.
Having spent a couple of hours on ebay I found a supplier of VITON O rings ( much better for unleaded) with a sizing very close to the original Honda size. Priced at £5.49 for 10) - great price.
Only a single O ring was used, assembled with a very thin smear general purpose grease to ease assembly when dry, and tested overnight with petrol in the tank, before refitting to the bike. It has now stood for 4 days with a 3/4 full tank and the sealing is bone dry.
I hope it may help others on the forum with same problem, I have posted below the name - details - and size Code BS018
This was purchased on their Ebay website
sealsuppliesUK
Imperial Viton Rubber FKM O Ring Seals 1.78mm Cross Section
BS018 - 18.77mm ID x 1.78mm C/S
Regards
Dennis
3
« on: November 03, 2024, 09:38:59 PM »
Hi All,
Took my CB400F for a trip along the Pyrenees, Bilbao to Barcelona but unfortunately fully complete the return trip.
The route I took meant the bike covered approx 750mi with a mixture of 30mph and 80mph roads - some riding was enthusiastic and some riding was cruising. The fuel I used was whatever standard e10 fuel as "super" wasn't always available.
At some point, the bike began overheating, smoking, had an unstable idle and would not accelerate past 60mph prompting me to cease riding for the remainder of the trip through fear of damage.
The bike was rebuilt some years ago using a mix of OEM/pattern parts (in particular the rings were aftermarket) and has covered approx 12000 miles.
Bike is back home and currently (slowly) in the rebuild process.
On dissassembly, there appears to be some minor damage to the pistons, rings, bores and head. (see the pictures attached). It appears to be localised to cylinders 2 and 3, cylinders 1 and 4 are visually ok and have good compression.
1. Any ideas on what could have happened or some ideas on what might have caused this situation? it would be pointless to rebuild and ignore this as it could happen again.
2. Are any of these components savlageable? The cylinders are actually smooth, can't feel anything by fingernail but there are a couple of dents. Probably due to the piston rings breaking up. Perhaps a rebore to 0.50 and use the DSS aftermarket piston/ring kit again?
As for the head, it does not look like theres damage (on initial look over) to the valves, valve seats or sealing faces - could this damage be removed with a rotary tool and tidied up? or is a replacement head necessary?
3. other misc information
- Engine oil used halfords petrol/diesel oils with a higher zinc content changed at 1200mi intervals.
- So far, it does not appear that theres been oil starvation. It looks like the head has been recieving plenty of oil but further inspection of the pump etc still needs to be done.
- Carbs have genuine jets and parts, no obvious signs of blockages etc.
- Genuine points ignition which appears to be adjusted correctly (via strobe light) and is functioning.
Hi Binman 180, ObservationsMy opinion FWIW 1.It looks as though the ring breakage through the groove, getting onto the top of the piston has caused all the peppering and marking to the top of the piston, head and cylinder wall. 2. The valve colour from combustion looks to be on the Weak mixture side, adding to piston crown temperature. 3. There are signs of burnt oil laquer around the piston upper half. See below an opinion I gave to a member regarding concerns over oil temperature. My gut feeling is that the centre 2 cylinders will run hotter simply because they are in the middle of a heat mass. "Hi, Having fitted both an oil pressure guage and temp guage to my CB400F some months ago, I can confirm that in normal riding you will easily be running at 95c + with 40ish psi @ 3000 and if you give it the beans for a few miles you will be at 120c with 15psi @ 3000. I suspect the reason a low 4.5psi oil pressure switch used was to prevent worry of riders seeing the light blinking at idle on a hot engine. It is likely that cylinders 2&3 are running even hotter.
**Piston temperature in the area of the ring grooves and piston crown will be well in excess of the 120c Oil temp.
IMHO If your seals and gaskets are newish, there is a definite case for synthetically improved oils** which wern't available in the day to handle the higher temp protection better, and I will be running some tests next spring. I think one of the major reasons for piston ring and groove failures is the deposits and gumming caused by burnt 10w 40 oil which cannot handle the excessive heat conditions at the top of the piston." Regards Dennis
4
« on: October 18, 2024, 05:51:15 PM »
My mileage these days is minimal, but I still replace the cable every two years. They sit very close to the cylinder head and gently cook. It's a slow process, and you don't really notice it until you fit a new cable. Absolute bliss!! On a similar note, my problem is with the return spring on the throttle, ye gods, I'm sure it would keep a barn door closed. Has anyone succesfully tried a lighter spring, and yes, this is with new correctly routed cables. When I tell my friends about problems with my right wrist allied to those caused by the railway sleeper saddle, they are starting to question my nocturnal habits!!!!!
I couldn't agree more Tric, Before my engine strip, when I disconnected my cable from the clutch housing I tried it for "freeness" by operating the lever and inner cable by hand. The result was VERY high friction and resistance. No matter what I did to try and free it (light lube etc) nothing improved it and it would not operate over its full range without tugging it with a pair of pliers. My conclusion was that the plastic lining that the cable is surrounded by, had actually patially melted and jammed as a consequence of being anchored too close to the cylinder head and fins by the Honda Guide.
Simple solution: Slide the clutch cable out of the guide and let it sit in its natural position, about 50mm further away from intense heat. No problem.
5
« on: September 20, 2023, 04:57:22 PM »
Hi, This tool available on Ebay Sealey Rubber Seal Gasket O-Ring Puller Remover removal Tool - AK7000 did a super job for me on the forks and would be versatile enough for other jobs.  Hope this helps. Dennis
6
« on: July 28, 2023, 09:32:46 PM »
If you need the choke to start a warm engine, it sounds like fuel starvation or excess air. Could be blocked jet(s), restricted fuel flow, vent blockage on tank. Excess air, could be flexible mounting rubbers leaking etc. Let us know how you get on. Dennis
7
« on: May 27, 2023, 10:45:11 PM »
Hi Sam, Sorry I couldn't get back to you sooner. Lifes very hectic at the moment and haven't had time to get back to mine yet  . In your circumstances I would just concentrate on getting the bike started after the rebuild of carbs on something like 1 1/4 turns on all carbs. Warm up the engine and set the throttle so it will idle near the normal idle speed. At this point turn each mixture screw 1/4 turn out and see if the engine slows down or speeds up. If it speeds up, (leaning the mixture) then reset the idle speed and do the same again, repeat the process until the idling becomes less even and slower (now too weak). Now go back to the sweet spot in between where it is the most efficient idle mixture setting for idle speed. Test throttle response for good pick up and give it a road test. Let us know how you get on. Hope this helps Dennis 
8
« on: April 24, 2023, 10:02:14 PM »
Ayup Dennis
Thanks for sharing your settings , I'm going to be using them for my bike. I have K&N with Delkavik exhaust. Currently my build has standard jets 75 40 and notch is in middle , bike is bogging down with full throttle. Hopefully your settings will be good for me as well!
Just wanted to clarify that I've adjusted the needles correcty? See pictures below . Top is original, bottom is new needle with one notch down. Is that correct?
Thanks again bud !
(Attachment Link)
Hi zombie365, Thats good timing I think. It just so happens that I decided to change my "Shorty" silencer late last year because it was a bit too obtrusive at full throttle. My choice was the Delkevic. A nice tonal balance and road legal. Your needle clips is in the same position as mine ie one below centre. You will see from my previous tests the Air/Fuel ratios which were recorded. What I have found since fitting the Delkevic is that it bogs down slightly when pullling out of roundabouts or sometimes when pulling away from traffic lights. The Air/Fuel ratio at say just above idle to 1/4 throttle has now gone significantly richer at 9.8:1 far too much for clean combustion. I haven't got around to the carbs strip and change yet, but my plan is to go for the 35 pilot jet to lean out the small throttle/intermediate opening and set the mixture screw to give around 13:1 for a clean idle. After this it will be down to road test and results. Due to shortage of time at the moment I am unlikely to be able to get back to it until late May - June. Check that your float levels are equal and true. Also that centrifugal advance system is working correctly on timing, to give correct full advance when checked with a strobe light. Retarded ignition will raise heat and reduce power. I would say that for me, the other Jet and needle settings I made still retained the good power and torque results, pulling strongly in 6th gear, with the Delkevic fitted. Let us know how you get on when you have set up and tested. Hope this help you, Cheers Dennis
9
« on: February 12, 2023, 08:08:53 PM »
Thanks Sesman and Ted.
After sticking it in the vice, applying a little heat, threatening it with long handled grips and lots of trial and error I've got to this.....
Hopefully that will be a lot better on the bike
What I found with mine after I removed it completely for inspection and light oiling, was that there were no kinks or bad bends, but that the inner lining must have melted and expanded causing the inner cable to bind, even after running oil right through. Worth checking if you stiil have some friction over the full travel before you refit it.
In view if this I have routed the new cable so that it does not go through the "Guide Eye" on the cambox cover, which will reduce any heat transfer from a hot cylinder head vicinity. Checking the cable after a good run confirms it is not getting hot now.
Dennis
Hi Guys, I was half asleep I think when I read it !!! It was the CLUTCH CABLE I was referrring to !!! Just testing to see if you were all awake  So just read it in the context of the clutch cable. Cheers Dennis
10
« on: February 11, 2023, 05:33:39 PM »
Thanks Sesman and Ted.
After sticking it in the vice, applying a little heat, threatening it with long handled grips and lots of trial and error I've got to this.....
Hopefully that will be a lot better on the bike
What I found with mine after I removed it completely for inspection and light oiling, was that there were no kinks or bad bends, but that the inner lining must have melted and expanded causing the inner cable to bind, even after running oil right through. Worth checking if you stiil have some friction over the full travel before you refit it. In view if this I have routed the new cable so that it does not go through the "Guide Eye" on the cambox cover, which will reduce any heat transfer from a hot cylinder head vicinity. Checking the cable after a good run confirms it is not getting hot now. Dennis
11
« on: February 03, 2023, 05:16:12 PM »
Unless the crank is new, the journals will be worn and you should be able to upsize to green
RogerxlixiAs well as physical instrument measuring, you should be able to get a final accurate clearance reading confirmed by assembling the bearing with "Plastiguage", then torqing to correct setting, then disassemble to read the actual clearance for each journal. Its a bit time consuming but gives a clear result IMHO. Dennis
12
« on: December 10, 2022, 09:07:57 PM »
Yes to that type of arrangement, but in agreement with you as to how effective it may be in cooling, I was referring to method of fixing as interesting point. The fit for F2 was this plus larger fins on head and barrels as complete package when they ran into trouble with lubrication on that model and kind of stop gap until the twin cam arrived in market.
Wondering the need for cooling as running oil too cold produces just as many problems as too hot. If you've no definite figures of your running example it may be worthwhile assessment to define this.
Running oil too cold, and especially at high rpm can bring unintended side effects. The pump is protected from hydraulic locking (virtually all engine have this) by a pressure bleed off valve that blows excess to sump effectively startng to starve key points in the lubrication system of supply, that's ordinarily the crank and big end bearing sites.
The flow is optimised for stated viscosity (varying with temp) at 90 degree C to give designed flow as originally tested and researched. You'd need to target this temp range in specifying cooling capacity.
I'm going to build a 460 engine for my bike, I have a spare 400 engine as a donor for the project and I now have most of the parts needed for the build, but I've read a lot of older posts claiming oil temp gets marginal with the larger bore size hence the need for additional cooling. I was looking to use an in-line oilstat to regulate the temp, being aware of the pitfalls of overcooling. (I'm an aircraft engineer by trade, spent decades working with both piston and gas turbine engines).
Hi,
Having fitted both an oil pressure guage and temp guage to my CB400F some months ago, I can confirm that in normal riding you will easily be running at 95c + with 40ish psi @ 3000 and if you give it the beans for a few miles you will be at 120c with 15psi @ 3000. I suspect the reason a low 4.5psi oil pressure switch used was to prevent worry of riders seeing the light blinking at idle on a hot engine.
IMHO If your seals and gaskets are newish, there is a definate case for synthetically improved oils which wern't available in the day to handle the higher temp better, and I will be running some tests next spring.
I think one of the major reasons for piston ring and groove failures is the deposits and gumming caused by burnt 10w 40 oil which cannot handle the excessive conditions at the top of the piston.
Regards
Dennis
13
« on: December 10, 2022, 08:51:31 PM »
Yes to that type of arrangement, but in agreement with you as to how effective it may be in cooling, I was referring to method of fixing as interesting point. The fit for F2 was this plus larger fins on head and barrels as complete package when they ran into trouble with lubrication on that model and kind of stop gap until the twin cam arrived in market.
Wondering the need for cooling as running oil too cold produces just as many problems as too hot. If you've no definite figures of your running example it may be worthwhile assessment to define this.
Running oil too cold, and especially at high rpm can bring unintended side effects. The pump is protected from hydraulic locking (virtually all engine have this) by a pressure bleed off valve that blows excess to sump effectively startng to starve key points in the lubrication system of supply, that's ordinarily the crank and big end bearing sites.
The flow is optimised for stated viscosity (varying with temp) at 90 degree C to give designed flow as originally tested and researched. You'd need to target this temp range in specifying cooling capacity.
I'm going to build a 460 engine for my bike, I have a spare 400 engine as a donor for the project and I now have most of the parts needed for the build, but I've read a lot of older posts claiming oil temp gets marginal with the larger bore size hence the need for additional cooling. I was looking to use an in-line oilstat to regulate the temp, being aware of the pitfalls of overcooling. (I'm an aircraft engineer by trade, spent decades working with both piston and gas turbine engines).
Hi, Having fitted both an oil pressure guage and temp guage to my CB400F some months ago, I can confirm that in normal riding you will easily be running at 95c + with 40ish psi @ 3000 and if you give it the beans for a few miles you will be at 120c with 15psi @ 3000. I suspect the reason a low 4.5psi oil pressure switch used was to prevent worry of riders seeing the light blinking at idle on a hot engine. IMHO If your seals and gaskets are newish, there is a definate case for synthetically improved oils which wern't available in the day to handle the higher temp better, and I will be running some tests next spring. I think one of the major reasons for piston ring and groove failures is the deposits and gumming caused by burnt 10w 40 oil which cannot handle the excessive conditions at the top of the piston. Regards Dennis
14
« on: November 29, 2022, 07:41:35 PM »
Hi Johnny, Moorey and Jezza, Thanks for your valued feedback its good to see the broader picture from everyone and see what experiences come in. Cheers Dennis
15
« on: November 29, 2022, 05:04:03 PM »
Dennis, I've just had a tank resprayed for my 400 and the sprayer (who only does tanks etc) said not to use POR or similar as I had a good tank. He said if the tank wasn't that good inside then a sealer would be better - who am I to argue!
I try and use Esso Supreme unleaded when I can and I'm sure that helps things.
Matt
Thanks for your reply Matt, Good to hear the opinion of a tank sprayer. I do use the Esso Supreme thanks, and last ride before winter I always add a very small amount of engine oil to any petrol in the tank and swish around to leave a layer internally. Like the diesel used or 2 stroke mix, this will help to resist rust formation. I'm interested to find out also because several members in our VJMC club swear by POR 15, but I feel it could overkill on a clean tank and if the treatment delaminates later it could cause other problems. Manufacurer claims seem to say it is OK up to 10% Ethanol content. We will see who else replies. Cheers Dennis
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